Avalanche Safety

Does Size Matter?

2012-01-25T12:34:00.000-08:00

I feel like a broken record.
I feel like a broken record.
I feel like a broken record.

Does size matter?

Here's an excellent video of a small avalanche.

Watch the video and draw your own conclusions about the relative safety of a small slope.

The slope in the video provides a perfect example of the concept of consequences. For any slope that contains enough snow for a complete burial, consequences are already at maximum regardless of the size of the slope.

Thanks to whoever posted this video. I assume that your friend is unhurt, and if so, it's great that you were paying attention because it doesn't take very much for situation like this to have an entirely different ending.

So, with that in mind, does size matter?

Does Size Matter?

2012-01-23T13:01:00.000-08:00

Hello from bed.

Two weeks of cold, sinus infection, and ear infection have kept me busy. It's even better when your family catches the same cold, and everyone gets sick ( and cranky ).

In light of the recent snow, and in light of some recent close calls, I'm going to post a link to a post I wrote in March of 2010. This post discusses the relationship between terrain size and our perception of hazard.

This is an important topic because, at one time or another, we've all traded horses and chosen smaller slopes that we thought were safer. But as the USFS pamphlet on avalanches clearly states, about half of all avalanche victims are killed by slides running less than 300 feet ( 90 metres ) slope distance.

Does Size Matter?

And while we're at it...

Let's have a quick refresher on uncertainty.

From Canada

2011-12-30T15:15:00.000-08:00

Here's Ilya Storm talking about avalanche education and recent conditions in British Columbia. ( And what a name! )

Avalanche Education

Current Danger Ratings in British Columbia

Snowpack Structure / Current Avalanche Danger

Triggers

Tunnel Creek

2011-12-27T11:33:00.000-08:00

Je ne peux pas vivre sans ta lumière, mais je dois essayer—proverbe Français vieux

A sad and information story about the Tunnel Creek avalanche that killed Riley McCarthy in March 2011. Thanks to Zap at Turns-All-Year for the link.

http://www.seattlemet.com/travel-and-outdoors/articles/stevens-pass-avalanche-december-2011/1/

The accident report from NWAC ( PDF ). I added "Tunnel Creek" to the Washington Terrain Ratings post.

Happy Holidays

2011-12-25T13:41:00.001-08:00

This CookieMonster wishes you happy holidays!

The Unconscious

2011-12-20T00:22:00.000-08:00

Fascinating and scary:

http://www.scientificamerican.com/article.cfm?id=probing-the-unconscious-mind

There really is something going on in our unconscious mind. Relevant for all you backcountry skiers who never skiied a line you didn't trust.

The Adirondacks

2011-12-18T16:12:00.001-08:00

Fascinating:

http://adkbcski.com/2011/12/12/adirondack-avalanches/

Enjoy!

Winter Science

2011-12-16T13:02:00.001-08:00

Just in case you haven't see this yet:

http://www.winterscience.com/

An amazing graphical representation of data from a weather station.

Leverage

2011-11-30T19:00:00.001-08:00

Once upon a time we fell apart, you're holding in your hands the two halves of my heart—Coldplay

AUTHOR'S NOTE: I've been slowly refining my thoughts on complexity over the last few posts. This should be the most useful summary so far. ( Post 1, Post 2. )

Perhaps unbelievably, you can use complexity to your advantage. Think of it this way: the more you know, the more you realise what you don't know. I was at a talk last year given by a famous researcher who summed up his career thus far in a few words: "In retrospect, it's clear that most of my career was spent learning how much I didn't know." ( Summary is mine. )

There is an on-going revolution in science that involves breaking down walls between departments in favour of multi-science approaches. In biology, this involves hiring computer programmers and statisticians. In the geosciences, it involves hiring psychologists and graphic artists. You get the idea.
After pondering for a few years, I'm going to propose a theoretical set of conditions that apply to learning about the avalanche problem. Rather than feeling confused—and I've certainly spent as much time as anyone dealing with confusion—I have come to believe that it's far easier to simply acknowledge the complexity ( and start dealing with it ).

Complexity is a great starting point. It nicely encapsulates the avalanche problem in simple terms that most people understand. By themselves, the scientific models of these systems are not terribly complex, but complexity arises when the systems begin to interact. Therefore, complexity describes the key difficulty involved in learning the science behind both the phenomena and the interactions of the phenomena that ultimately create a new system.

Read this thread on turns-all-year that discusses the complexity of accident formation. Again, by complexity, I mean novel phenomena, de novo outcomes, and small changes having significant affects.

Figure 1.1. Simulation of wind encountering a very simple mountain barrier. Consider the effects of turbulence. What might you see in actual mountain terrain?

wind rotor simulation from Lundeee on Vimeo.

Figure 1.2. Time-lapse of clouds, mountain, and sunlight. The lapse allows us to see the scale and complexity of the phenomena. What patterns would you expect to find based on the prevailing wind direction?

Figure 1.3. Time-lapse of clouds, mountain, and sunlight around Pike's Peak, Colorado, United States. The lapse allows us to see the scale and complexity of the phenomena. Notice how the patterns of light and shadow from the clouds defy simple descriptions of solar input by aspect. Can you imagine the complexity of the heat flux in this environment?

Figure 1.4. We're complex too.

Figure 1.5. Transcription and translation. It's amazing that this even works, but remember, we're complex too.

Figure 1.6. Cognition. My mind, it's blown.

Strategies

Let's start with a set of concepts that work in both the theoretical and applied spaces. ( In this example theoretical and applied spaces means: "people who think about it, people who do it, and people who think about it and do it". )

The concepts are as follows:

1. The mountain environment is a system of complex phenomena.
2. We are a system of complex phenomena.
3. Various scientific models promote awareness of these phenomena.
4. The interaction of these complex phenomena forms another system.
5. Theoretical and applied models of the whole system are missing1.

Current strategies for managing the complexity inherent to the avalanche problem:

1. Rules are an appropriate simplification of complexity.
2. The public avalanche bulletin is an appropriate simplification of complexity.
3. Uncertainty is an appropriate simplification of complexity.

Figure 1.7. Other strategies for managing situations of varying complexity. This framework presents several levels of complexity and suggests a different approach for each situation.

Figure 1.8. A video explaining how the model works. The framework's designer says that we approach situations with our default viewpoint, and this leads to bad decisions. Instead, we should evaluate the situation and choose the best approach rather than what we prefer.

Does anyone else's brain hurt?

1 The avalanche triangle is a great model but it does not formally address complexity.

Simplification

2011-11-29T16:37:00.001-08:00

With friends surrounded, the dawn mist glowing, the water flowing, the endless river, forever and ever—Pink Floyd

AUTHOR'S NOTE: The last post was complicated and rambling, so I'm going to present a careful simplification. I also feel the need to explain something else: for a long time I've written about uncertainty and some people have asked about alternatives. So, if you think uncertainty is too general, you get to deal with complexity instead.

1. Natural phenomena are fundamentally complex.
2. Scientific models of the phenomena are not particularly complex.
3. Mixing in the scientific models, as with mixing in the real world, introduces complexity.
4. Complexity in the models is simply a reflection of the original, irreducible complexities.

We're told again and again to use multiple observations before making decisions. Surely this means that a systems understanding is the best approach to mountain safety. One way to approach it from a systems level is to simply acknowledge the incredible uncertainty, but there are other approaches.

You can approach the problem from the perspective of thermodynamics. Is this a requirement? No, but some people prefer this approach. You can approach the problem from the perspective of psychology. Is this a requirement? No, but some people prefer this approach. What about a risk management approach? Rule-based approaches?

Clearly there are numerous approaches, and if we follow the rule of multiple observations, then it's obvious that we need to use techniques from each area.

Of course new complexities arise as soon as we start mixing the models of thermodynamics, psychology, and uncertainty.

And you've already heard that story, right?

NOTE: There are great new features from http://www.hillmap.com/. Please read this post on Turns-All-Year for instructions on using this exciting product.

Integration

2011-11-28T17:35:00.000-08:00

At a higher altitude the flag unfurled, we reached the dizzy heights of that dreamed of world—Pink Floyd

AUTHOR'S NOTE: A few weeks ago, I wondered what was behind my recent spate of posts. After some reflection, it's clear I've been searching for a theme for the 2011-2012 ski season. Past themes have included uncertainty and psychology, but this year I'm going to write about complexity. Very often complexity is managed by breaking things down into constituent elements. As we shall see, this has benefits and drawbacks.

This post compares simplicity with complexity; specifically whether or not it is desirable, possible, or necessary to simplify complex information. This post will require significant patience, so if you're not feeling patient ... please come back when you are.

Experiment #1

Maybe you don't often think about linguistics, but it's pervasive, and you rely on linquistic techniques every time you read, write, and communicate. In this experiment, we're going to borrow a few tricks from linguistics and engage in a thought experiment or two. Consider the following sentence:

The snow is between the sky and the ground.

Figure 1.1. The sentence is a system composed of individual elements ( called words ) and we could say that meaning emerges from the system. Spend a moment thinking about alternate word arrangements. While you're at it, take a long, hard look at the sentence and see if you can extract additional meaning from the arrangement of the words. Does rearrangement affect your perception?

The ground and snow are below the sky.
The sky is above the snow and the ground.

Figure 1.2. What about removing individual letters? Sometimes it matters and sometimes it doesn't, but having not seen the original, how many people can reconstruct the original phrase from the phrase below?

The now is betwen he ky an te grond.

Figure 1.3. If removing letters doesn't work very well, what about reducing the system to its constitutent elements? You can still extract meaning from the individual words, and it may be possible to extract a general concept from the words themselves. But ask yourself, do the individual words have the same meaning as the original or has something has been lost in the simplification? How would you describe the change in meaning for this diagram?

And
Between
Ground
Is
Sky
Snow
The

Figure 1.4. What about the individual letters? Do you feel like this representation is much simpler than the original sentence? If so, you can test the hypothesis by comparing the time required to memorise the string of letters with the time required to memorise the original phrase. One thing we can say for sure is that the original meaning has been lost entirely. Still, the individual letters are very easy to understand in the sense that you know what the letters themselves represent. How would you describe the change in meaning for this diagram?

A, B, D, E, G, H, I, K, L, N, O, R, S, T, U, V, W, Y

Figure 1.5. I hate to take you back to grammar school, but this is a diagram of the sentence. It's another model of the system and it gives you an idea of how to simplify the system in a way that preserves its essential meaning: snow between sky and ground. If we want an even simpler representation, we can use the following: sky snow ground. In this case, we've kept the three essential nouns and we're encoding the position of the snow ( between ) in the structure of the phrase itself. Neither simplification constitutes a proper sentence, but we aren't interested in grammar at the moment. As it turns out, the really essential elements are three nouns, but counter-intuitively, adding an adjective and a conjunction significantly increases understanding. All this might sound nutty, but you probably do it almost every day. How many times have you revised an email and wondered if you're still getting your point across? Do you add or remove information to simplify and increase clarity? My guess is that you do both.

Off The Philosphical Deep End

Well not really, but here's a question that seems very philosophical: why does writing work? How is it possible to take 26 characters and produce the works of Shakespeare, The Avalanche Handbook, and this blog? The science of physics provides a very reasonable answer.

Writing works because of a concept called mixing. The origin of mixing depends on who you ask, but classically, mixing is used to describe irreversible processes such as mixing ink in water or mixing vodka, water, and vermouth. Literature, which is an execellent example of complexity in its own right, emerges from the alphabet because we can mix the letters into words, we can mix words into phrases, and we can mix phrases into sentences. You can even mix letters and make up your own words, which might sound a little ridiculous, but it happens every day.

But anyway, this is where scale comes in.

In addition to the concept of meaning, we are also working with the concept of scale. Where is meaning encoded? At the scale of a sentence, clause, word, or letter? Actually, meaning is encoded at all scales. A is not the same as B just as apple is not the same as bat and I like apples is not the same as I like bats. Yes, you can file this under useless philosophical controversies, but it's quite true nonetheless.

This blog post also exploits mixing. Not only am I mixing letters, phrases, and words into a novel work, I am also mixing concepts from linquistics, physics, mathematics, and meteorology. But let's go back to the word exercise for a moment: you can see that simplifying a system doesn't always make it easier to understand.

So, why is that?

When you simplify something, you create something novel, and there is a very significant chance that new complexity will emerge from your novel creation. In many cases, the complexity that arises from simplifications actively prevents clear understanding. Sound like a stretch? Go back to the sentence experiments and do them again.

Or just ask yourself how many times you've requested clarification from the author of a five word email.

Experiment #2

This experiment is designed to test your patience ( and powers of observation ).

Figure 1.6. Watch this video of the environment, but pretend that it's snowing and you have magical binoculars that allow you to see through the storm. Rather than thinking about terrain, snowpack, and weather, just think about the environment containing the terrain, snowpack, and weather. The interaction between the systems produces remarkable variations.

Write three words that describe what you've observed. Mixing makes things quite complicated, doesn't it? Three words aren't quite enough? Alright then, start by explaining the phenomena you've observed with a single sentence of up to 10 words. If that's not enough, then feel free to use a paragraph. If you still feel constrained, use three paragraphs: introduction, body, and conclusion.

Samples

Here are several sample models of the phenomena at play. Mixing is represented by the arrows, and the on-going nature of the phenomena are represented by the continuous cycle diagram.

Figure 1.7. Here's my three word version of my observations from the video. You'll notice that it's wrapped up in a conceptual model that integrates the elements. I spent a week thinking about this and actually consulted several outside experts. By itself, this model is very easy to understand. But as in the real world, the factors in this diagram are mixed with the factors in the following diagram.

Figure 1.8. Here's a model of what's going on in the snowpack. Again, by itself snow metamorphism isn't particularly difficult to understand. And again, complexity arises because the factors in this diagram are mixed with the factors in the preceding diagram and the following diagram.

Figure 1.9. Here's a model of what's going on with the weather. When viewed alone, these weather trends are very easy to understand. But again, complexity arises because weather factors are mixed with factors from the preceding diagrams. This means that, ultimately, the direction of instability corresponds to the magnitude, rate, and duration of each factor, which is determined by a complex mix of other factors ( and so on ).

This post probably seems a bit strange, but I want to make a point.

Simplicity and complexity are not mortal enemies. They're not at opposite ends of a spectrum. In fact, comparing simplicity with complexity is like comparing apples and oranges. As a backcountry skier, it's important to ask yourself if you really understand the sources of complexity.

HINT: It's not the science.

Spindrift

2011-11-28T14:26:00.001-08:00

I was in a similar situation once in British Columbia. Nothing as dramatic as the video below, but it was scary. No wonder I hate ice climbing.

Video:

Full story:

http://willgadd.com/?p=600

Fast Thinking

2011-11-22T01:52:00.001-08:00

Daniel Kahneman is an incredible thinker. If you have interest in "human factors", this video is a must see.

http://www.guardian.co.uk/commentisfree/video/2011/nov/21/daniel-kahneman-psychology-video

Northwest Snow & Avalanche Summit Download

2011-11-14T17:36:00.001-08:00

On Sunday, I gave a presentation at the Northwest Snow & Avalanche Summit.

Here's a link to the presentation.

In Honour of Monika Johnson

2011-11-11T18:14:00.001-08:00

Glowing Sun, Bright Sun—Sigur Ros

From turns-all-year.com:

Our community suffered a huge loss last year when Monika Johnson broke through a cornice on Red Mountain, February 1st, 2011. In her honor, a group of her good friends and family have started The Monika Johnson Avalanche Education Scholarship, a.k.a. The Yuki Awards.

Learn More at Turns-All-Year

REI Avalanche Safety

2011-11-08T17:52:00.000-08:00

If you could read my mind, what a tale my thoughts would tell—Gordon Lightfoot

REI has an interesting feature on avalanche safety. My criticism in a single sentence: it's a disconnected collection of "rules of thumb" punctuated by errors, some of which are significant. It's clear the authors know something about snow safety... but... not quite enough.

From the first page in the series:

During winter, a south–facing slope is more stable than a north–facing one since it has sun exposure to melt and condense the snow. The tempting north–facing slopes that hold all the best powder are also more likely to have unstable layers of ’depth hoar,’ the dry, icy snow that does not stick to the adjacent layers. Since these slopes don't have the benefit of sun to warm and compact the snow over the winter, they tend to be less stable than south–facing slopes.

This is not true. Instability can develop on any slope, at any time during the winter. In fact, The Avalanche Handbook, citing research by Grimsdottir, plainly states that, after accounting for slope use patterns, aspect is a poor predictor of avalanches. You should never use aspect by itself to judge instability, and the beginners at whom this article is clearly targeted need to know this more than the experts.

Also from page 1 of the series:

A common crystal type that is particularly dangerous due to its inability to bond with other snow crystals is know as ’hoar.’ Hoar snow, also called ’sugar snow’ because of its similarity to granulated sugar, can be found at any depth or at multiple depths in a deep snowpack.

"Hoar" isn't really the correct term. The author should refer to facets, surface hoar, and depth hoar, or refrain from using any terminology except for "sugar snow" or perhaps "coarse snow". The other problem is that very fine layers of facets ( such as facets above or below a crust ) can be very easy to miss. The difficulty in identifying thin weak layers should be noted in the article.

Also from page 1 of the series:

Snowstorms pile up one after the other all winter long. Wind blows snow off of some slopes and on to others. Temperature changes cause snow crystals to metamorphose. If the snow’s consistency remains constant, the snowpack is homogenous and stable. It’s when the snowpack develops different layers of different snow types that it becomes unstable and hazardous.

This paragraph started out so well... Unfortunately, the statement about constant consistency being an absolute measure of "stability" is entirely wrong and dangerously misleading. First, snowpack evaluation is framed around the search for instability, and second, a beginner should not judge the stability of the snowpack by consistency alone because it is very easy to miss important signs of inconsistency. Better to err on the side of caution if you just don't know.

From the second page in the series:

Dig a pit 5 feet deep or to the ground (whichever comes first) on an open slope after probing to see if there is any old avalanche debris, rocks or brush in the way. Make the face of the pit smooth with your shovel.
Use a glove to brush the surface of this wall to see if there are visible layers.
Use a credit card or driver’s license and, holding it lightly, slide it down the wall. Notice where the card catches on hard layers.
Do the same starting at the bottom and sliding up.
Next, do a finger test for soft layers, running your gloved hand first down and then up the wall. Note where the hard layers (possibly sun or wind crust) and the soft layers (depth hoar) are located.
If you don’t detect any significant layers in the snow, you can continue on your trip. But if there are crusty or soft layers, you should then perform at least one of the following tests.

This isn't really the correct procedure for performing a snow profile, although it clearly tries to communicate the right information. Use a driver's license or credit card? It would be better to provide an explanation of how to excavate the profile and use simple tests to evaluate layering and determine if hardness increases with depth. There is a very strong relationship between data sampling and perception of instability, and the rudimentary tests discussed here could miss important details. It's better for most recreational backcountry skiers to avoid formal profiles and focus on snowpack tests instead ( which are outlined on the page ).

Also from page 2 in the series:

The Rutschblock test is fairly reliable in predicting fracture initiation (how much force is required to start an avalanche). The Extended Column Test has become more popular because it not only predicts fracture initiation, it includes fracture propagation (how big the avalanche might be). The ECT is also easier to perform since the size of the isolated block is smaller.

Shear quality analysis derived from rustchblock tests can also provide valuable information about fracture propogation. It is worth mentioning that the ECT most certainly DOES NOT predict avalanche size, and even if it did, most people are killed by small avalanches that don't travel very far.

Also from the page 2 in the series:

If you have to jump in the middle of the block, there’s likely a low chance of avalanches on slopes with similar angle and aspect.

This is only true if you ignore spatial variability.

Also from the page 2 in the series:

A Q1 shear is of more concern to the backcountry traveler than a Q3 shear.

First, this is non-information, and second, after spending most of the page discussing how to perform snowpack tests, the author neglects to discuss the importance of shear quality. Not only that, but Q1 and Q2 shears have roughly the same importance with respect to skier-triggered avalanches. Here's the skinny on shear quality for beginners: if you observe shears that are rapid, sudden, or smooth, then you have uncovered a clear sign of snowpack instability.

Anyway, I want to be clear that this is not an attempt to criticise REI, but at the same time, it would be very easy for REI to check this information with a local guide service.

Northwest Snow & Avalanche Summit

2011-11-04T10:28:00.000-07:00

Have you heard about the Northwest Snow & Avalanche Summit? Hosted by Michael Jackson, there will be speakers, presentations, food, and lots of talk about snow avalanches. I'll be there giving a short presentation, but you should really come and see Garth Ferber, Karl Birkeland, Rod Newcomb, and Karl Klassen.

http://www.brownpapertickets.com/event/199594

There are some tickets still available, but it is unlikely that any will be available at the door. Feel free to come say hello, especially if you happen to have spare cookies!

Knowing, Part III

2011-11-02T19:02:00.001-07:00

I get this feeling I'm in motion, a sudden sense of liberty—New Order

In the last few posts I've made a lot of noise about sources of uncertainty, and I've tried to illustrate the science behind the uncertainty. In this post, I'm going to try and illustrate things that can be measured accurately.

CAUTION: These are research images, and as such, they are not suitable for route selection, navigation, or any other "real world" application. I have presented similar maps in another blog post, but those maps intentionally have certain features removed to preserve uncertainty. These maps contain statistical analysis that can significantly alter your perception of the terrain therein.

Figure 1.1. This is a map of avalanche terrain, non-avalanche terrain, convex, and concave surfaces for Asulkan Valley, Glacier National Park, British Columbia. I think the variations are fairly obvious. These notes are a few years old, and yet the concept of variations underlies the discussion.

Figure 1.2. This is a map of cumulative slope angles for Connaught Creek, Glacier National Park, Canada. The cumulative slope angle provides a rough index of several variables: avalanche terrain, surface area, and overall exposure.

Figure 1.3. Map of avalanche terrain at Avalanche Crest, Glacier National Park, Canada. For the regions enclosed in red-lines, varying degrees of avalanche terrain are indicated with red shading. Non-avalanche terrain is indicated with blue shading. ~70-90 percent of the terrain in the upper regions is avalanche terrain.

The distribution of avalanche terrain shows us why avalanches from the huge, central start zone do not reach the Trans-Canada highway; non-avalanche terrain below the bowl creates a runout zone. In several cases, the presence of known runouts correlates exactly with large patches of non-avalanche terrain.

Runout locations are often found on areas with very light blue or almost white patches. ( Correlation verified with terrain rating materials from Parks Canada. ) Additional small patches of non-avalanche terrain below the planar start zone probably serve as runouts for smaller avalanches — and as abrupt slope angle terrain traps.

Figure 1.4. Surface area values in square meters for terrain at Avalanche Crest. The length and width of each cell is approximately the same size ( +/- 3% ). The larger surface area is a factor in start zone formation and density of start zones. The surface area difference between 651,182 and 485,899 is 165,283 square meters; the equivalent of 400m×400m of additional surface area.

Stated simply, large quantities of snow accumulate in the start zone because the surface area is greater by almost 1/4 square kilometer. Remember, areal size is the same ( if compared on a map ) but surface area in the start zone is much greater because of surface curvature.

Assuming each area is subject to 1-meter of snowfall, weighing 200 kg / cubic meter after metamorphism, accumulation in the runout zone is around 91,000,000 kilograms of snow; accumulation in the start zone is around 130,000,000 kilograms. That's a difference of ~40,000,000 kilograms. In many cases, local wind-effects may cause an increase or decrease in snow supply but this is impossible to measure at present.

Figure 1.5. Statistical analysis that compares cumulative slope angles from model runs to distribution curves taken from terrain rated by humans. The distribution curves are derived from statistics of terrain that has already been rated. This approach is best described as "nearest neighbours". At the time this image was prepared, I had not yet completed the statistical modeling for "Simple" or "Challenging" terrain. The final distribution curves closely matched my speculative sketches.

Knowing, Part II

2011-11-02T19:02:00.000-07:00

I was just guessing at numbers and figures, pulling the puzzles apart—Coldplay

( AUTHOR'S NOTE: This is the nine-thousandth post that addresses the general question of Why Is It So Complicated? While teaching often involves simplification, it's important to remember that you can also use complexity to teach. Despite conventional wisdom, complexity is not always the enemy of simple, and simplicity does not always improve understanding. This post is not meant to be a primer on statistics; it is an attempt to use simple statistics to illustrate the complexity of avalanche problems. Finally, this post does not apply to professional avalanche forecasters because they possess a.) a giant mental database of distributional information, b.) detailed information about the current situation, c.) access to high-end computer models, d.) extensive knowledge about the interaction of terrain and weather in the forecast areas. )

The question: why should we avoid speculating about whether or not data from one location can be used to estimate values at another location and simply acknowledge the uncertainty instead?

Do you really want to know? Here's an answer that goes a bit deeper than "because". I'd like to think that this answer goes all the way to the bottom of the rabbit hole, but unfortunately this particular rabbit hole is very deep.

Introduction
When we discuss avalanches, we often talk about observations. When we discuss observations, we are talking about data. Maybe it's wind speed and direction or precipitation intensity. Or maybe it's shear quality and cracking. Either way, we most often relate the data to a specific place, which is a process referred to as spatialisation. Places are described with a frame of reference such as aspect, elevation, or perhaps something as simple as a name.

Now, let's think of the observation as a single sample at a single point in space. Most of us are immediately curious to know whether or not we can use the data to estimate values for another location. With backcountry avalanche forecasting, the answer is usually no, and a fairly simple principle outlines the complexity:

variations = uncertainty

There are variety of words that describe variations, including homogeneity, heterogeneity, variance, invariance, isotropy, and anisotropy, but we'll just stick with variations for the time being.

Examples
Don't worry these figures, and the accompanying text, make my head hurt too.

Figure 1.1. Consider the terrain shown below. It's not really perfectly flat, and its surface is composed of different materials. However, there are some important ways in which variations in the terrain are low: the maximum difference in elevation is small. But even with such a simple shape, the interaction between terrain and weather still produces a chaotic arrangement of snow depths, drifts, crusts, and weak layers.

With that in mind, can we use a data sample from one location applicable to estimate the value of data at another location? Provided you can account for a significant degree of uncertainty, including the randomness inherent to the chaotic/complex system that produced the snowpack, then yes, you can use data from one location to estimate the values elsewhere.

Figure 1.2. The next example shows some mountainous terrain. The variations in the data are fairly obvious: the maximum difference between elevation values is much greater than in Figure 1.1. These variations create other variations such as orientation to the sky and orientation to wind. ( Which is similar to "propogation of uncertainty" in formal statistics. )

Start to imagine how these variations affect our ability to use a value taken at point A to estimate the values at points B and C. We have our frames of reference such as aspect, elevation, and temperature, but these are simply ways of sorting the data into buckets. A frame of reference can simplify how we perceive the data, but a frame of reference does not reduce the frequency of variations, nor their magnitude.

Figure 1.3. Here's a histogram of the elevation values in the second image ( blue ). You'll notice the magnitude and frequency of variation are statistically significant. Remember, the key equation is variations = uncertainty. If it's of interest to you, the standard deviation is ~210, which is quite a large value for this data set. The histogram for the first image ( red ) has been fit into the same graph. There is much less variation.

Despite the variances, it's important to note that the data set itself is relatively stable. This simply means that, for our purposes, the values in the set aren't going to change very much in our lifetime. This is why experienced avalanche forecasters often say that terrain is the solution to a dirty snowpack. The stability of the data set reduces certain types of uncertainty.

NOTE: I'm going to make an important point about "making things simpler" and about the dangers of using speculation to estimate the value at two locations from a single piece of data.

Figure 1.4. So we've got a complex problem... we need to simply things... right? The thing is, simplification often has incredibly serious side effects, some of which are outlined in this example. This image shows an accurate simplification of the terrain produced with combination of mathematics and computer science called computational geometry.

Accuracy of the simplification aside, if we look at the image and consider the data at each point, it's immediately clear that a lot of data are missing. Missing data doesn't tend to make things easier, and in some cases it can be downright dangerous. Remember, simplification removes data, so while everything in the model is simpler, our picture is far less complete. Can we fill in the gaps?

There are hundreds of ways to accomplish this using everything from basic math to empirical statistical approaches. Do you favour linear interpolation? What about inverse distance weighting? Kriging? Unfortunately, even if the accuracy of the approach is reasonable, so much uncertainty remains that the simplification doesn't really help very much. Here's why:

Very often, simplification helpfully reduces data while unhelpfully introducing novel variations that are difficult to measure ( which increases uncertainty ). Simplification can reduce complexity, but only when implemented with fanatical attention to detail. This requires to understand all the details and side-effects of your simplification in a way that you can quantify to a high degree of accuracy.

Otherwise, you will certainly end up with less data, but new uncertainties will propogate through your "simplified" model. Think of it this way: before, you were uncertain ( but you knew why ) and now you're uncertain ( and you don't know why ). Imagine trying to use your brain to take the value of A and accurately determine the values of B and C. Does it still seem like a good idea?

Figure 1.5. This is a map of the drainage network for the terrain near Crystal Mountain Ski Resort. For the purpose of illustration, pretend for a moment that this is a map of wind directions that accurately depicts wind flow over rough terrain for a single second during a five hour storm. ( A sampling rate of 1:18000, which is laughably low. )

If you want to imagine what this would actually look like during our hypothetical storm, think about each arrow rotating and increasing/decreasing in size. However, in a rather beautiful paradox, even if you could somehow make the wind flow simulation accurate ( which you can't ), you'd still be wildly uncertain about actual snowfall amounts.

Of course, the next step involves adding clusters of snow crystals to the simulation, and suddenly it would be nice to have a supercomputer. This obscene complexity is simply business as usual for complex systems such as weather and its interaction with terrain. This image makes it pretty clear why local snowfall accumulations often have a variance of 1:10. Ten times more accumulation at point A than point B.

Figure 1.6. Don't worry, it gets worse! This is an overhead map of "Cement Basin" near Crystal Mountain Ski Resort, Washington State. This map shows ground cover such as trees in black, and open areas in white. Surface hoar forms best in areas with a clear view of the sky ( white ). How do ground cover variations effect your perception of where surface hoar forms?

What about variations in crystal size? Think about the gray areas where surface hoar crystals are small, but still connected to areas where the crystals are large. Do you think it's possible to figure out a safe route, or are the variations simply too complex? Are you sure of your ability to collect empirical estimates, or would you rather accept the uncertainty ( and deal with it )?

Variations Are a Fact of Life
Can we overcome the uncertainty inherent in data with large variations? Unfortunately, in the context of backcountry avalanche forecasting, the short answer is that we can't, and managing this inherent uncertainty is what professionals refer to as managing the risk. While this sounds vague, managing the risk includes reducing exposure to variation in order to reduce the amount of uncertainty.

And fortunately for us, it's utterly trivial to reduce exposure to variation.

Figure 1.8. This is a map of "Cement Basin" near Crystal Mountain Ski Resort, Washington State. This is a tiny drainage, but it still contains significant variation, and it's certainly a very easy place to get injured or killed in poor conditions. So, whether you're new to the backcountry, or an old dog in search of an easy day, always remember that you can reduce variations by choosing very small slopes. Just don't let the size of a slope lull you into a fall sense of security.

Geostatistics
Empirical solutions to the problems discussed above belong to a domain called geostatistics ( which is one of my professional interests ). I can rattle on about this domain all day long if you wanted, but I still won't be able to give you any clear answers, and I'm pretty sure you don't want me to rattle on all day.

The clear answer is that interpolation of spatial data derived from chaotic/complex systems is extremely tricky business. That's why this problem has been boxed up nicely inside the concept of spatial variability. Yes, there are things you can know: research has established that there is less variability to shear quality than the number of taps applied during a snowpack test. You can also know the general character of new snow amounts or precipitation intensity.

But it's important not to confuse hard data with speculation. Very often, it's easy to take hard data and try to apply it elsewhere without accounting for the uncertainty that comes with natural variations. This is when science becomes speculation, and while speculation isn't inherently wrong or dangerous, there are definitely situations when it can lead you down the garden path to somewhere you don't belong.

And you can be certain of that.

Knowing, Part I

2011-10-31T19:53:00.000-07:00

I could feel at the time, there was no way of knowing—Roxy Music

From Wikipedia: Holism (from ὂλος holos, a Greek word meaning all, whole, entire, total) is the idea that all the properties of a given system (physical, biological, chemical, social, economic, mental, linguistic, etc.) cannot be determined or explained by its component parts alone. Instead, the system as a whole determines in an important way how the parts behave.

In my last post, I outlined some priorities for learning snow safety. I'd like to provide a few additional simplifications.

A.) Understand yourself and the people with whom you ski.
B.) Develop a mental model of the physical processes taking place in the mountains.
C.) Integrate A and B via correct backcountry avalanche forecasting procedures.

Once you have some basic information, you can start to apply correct backcountry avalanche forecasting procedures to "the avalanche problem", and produce further refinements. You can boil backcountry avalanche forecasting down to its essence in the following manner:

The goal of backcountry avalanche forecasting is to minimise uncertainty about instability by prioritising information acquired through an understanding of the physical processes taking place in the mountain environment while accounting for the possibility of human error.

Of course, all of this is much easier said than done, especially since there are always shortcomings in the data. In terms of cognition, these shortcomings combine with well-known limitations of our psychology and variations in our perception to blunt our awareness and numb us to the effects of uncertainty.

All of which ultimately increase our vulnerability to serious errors. Following correct procedures greatly reduces the chance of error ( and the consequences ).

It's the difference between knowing and not knowing.

2011-2012 Avalanche Season

2011-10-28T01:08:00.000-07:00

I guess it's the price of love; I know it's not cheap—U2

Author's Note: Okay, as a "treat", I've written a grand ramble.

Part I. The Dynamic Nature of Backcountry Avalanche Forecasting

Backcountry avalanche forecasting is concerned with minimising uncertainty about snowpack instability at a specific time and place. Recreational backcountry skiers are very good at making observations, but often seem confused about how to prioritise their observations. Here are some rules and regulations:

Datum	Description
Class III	Weather Factors. Mostly numeric data; there is high uncertainty about the relationship between weather data and avalanches. This includes observations such as warming, cooling, wind direction, new snow, and rain. The snow may or may not be unstable.
Class II	Snowpack Factors. Mostly rule-based data; medium uncertainty about the relationship between snowpack data and avalanches. Includes the results of instability tests ( especially shear quality / fracture character ), snow profiles, ski testing. Are there signs of instability? Is skier-triggering possible?
Class I	Instability Factors. Mostly event-based data; low uncertainty about the relationship between instability factors and avalanches. Cracking, whumpfing, avalanches. Skier-triggering is possible. Is there a significant chance of releasing an avalanche of Size 2 or greater?

Weather Examples
If there is heavy accumulation of new snow, with wind, and warming, and whumpfs, then I'm going to be super careful because I know the snowpack is unstable. However, at this point I don't really care about the heavy accumulation, the wind, or the warming. I'm only concerned with the whumpfing, because it is a crystal clear sign of high snowpack instability.

In this example, I've given the most weight to the observation that reveals direct information about instability. It's also worth mentioning that whumpfs can occur with new snow, cold temperatures, and calm conditions. The endless variety of parameters and outcomes is why weather data has an inherently uncertain characteristic.

In the absence of direct signs of instability, I'd give the most weight to whatever observations revealed the most information about instability. In this example, I would assign a higher priority to recent wind/warming than to new snow amounts because wind can turn small accumulations into thick wind slabs and warming can destabilise the existing snowpack. This is one place where a well-rounded understanding of mountain weather, along with the physical properties of snow, makes prioritisation much easier.

Snowpack Examples
In the case of snowpack factors, I would assign higher priority to shear quality / fracture character than to the number of taps in a compression test. Mostly because the number of taps only provides indirect information about instability ( an index of instability if you will ), whereas shear quality/fracture character reveals fairly direct information about instability. I use the extended column test in a similar fashion. It's important to note that research in Canada ( by Cam Campbell et al. ) has found that there is less variability with respect to shear quality than for the number of taps.

The Avalanche Handbook compares improper use of snowpack tests to the lottery and Russian roulette. For this reason, and for other reasons that I won't discuss here, I really don't use snowpack tests or formal profiles all that often because I'm really only looking for a few specific things when I dig:

What is the layering?
What are the crystal forms?
Does hardness increase uniformly with depth?

I perform formal snowpack tests only when I'm curious about the shear quality and fracture character of something specific. Very often, finding a weakness is enough to make me strongly consider alternate plans without the need for actually testing the weakness. I suppose this is my way of saying that I assume it is possible to release avalanches on most weaknesses.

For the record: I'm providing this information here as an example of how I prioritise observations and sort out red flags; this is just my personal style. You probably shouldn't do things this way unless you understand snow metamorphism from cloud-to-ground.

Backcountry Avalanche Forecasting Is Dynamic
Anyway, this leads to the next concept: the dynamic, ongoing nature of backcountry avalanche forecasting is one thing that quite a few recreational backcountry skiers don't understand very well. I have actually witnessed backcountry skiers comparing and contrasting signs of stability with signs of instability. Backcountry avalanche forecasting is framed around instability, and searching for signs of stability ( AKA "searching for supportive evidence" ) amounts to doing it backwards.

And feel free to disregard redundant information: research by Makridakis shows us that while additional information can increase your confidence in a conclusion, the relationship between confidence and accuracy is tenuous. Futhermore, Makridakis found that redundant information can actually decrease the accuracy of predictions. The correct procedure: continually revise your forecast as you integrate new observations. Continually ask yourself, using the data interpretation guidelines above, does the data reveal anything about instability? A single piece of data that reveals information about instability has the power to completely change the forecast from "potential instability" to "high instability". New plans are in order if that's the case.

Regardless of any of my prattling, make conservative decisions when your uncertainty is high for any reason. High uncertainty is a sign that you lack the information required to make sound judgments about risk. And remember, desire and uncertainty are an especially dangerous combination when unmanaged.

The rest of the post contains musings and additional information. There is a lot of opinion, so please take it with a grain of salt.

Part 2. How Do I Learn Snow Safety?
Okay, it's time to get out the salt. Keep the salt out until the very end of this post.

Having resumed posting for the season, people have started asking questions about how to learn snow safety. With good reason, most people will never have the interest in or need to develop a professional level understanding of snow safety, but that doesn't mean they aren't interested in gaining a deeper understanding. Maybe it's because they love powder skiing, ski mountaineering, or powder skiing mountaineering. Maybe it's because they love their friends and family.

I'm not sure how to answer this question because I learned snow safety through a blend of frozen fingers, the terror of bad decisions, and lots of studying. If I had to do it all over again, I'd set the following goal: develop a reasonably detailed mental model of the physical processes taking place in the mountain environment. Here are the main study areas:

Learn About	Description
Yourself	Invaluable since we create the hazard. Incredibly difficult. Easily #1. ParksCanada has maps of popular backcountry skiing locations and one of maps actually asks the user "what brings you here today?". In a similar vein, Martin Volken gave a talk at the 2008 Northwest Snow & Avalanche Summit. His presentation asked "why are we going to the mountains?" It was a wonderful talk.
Snow Metamorphism	From cloud to ground. Utterly invaluable. Better learned while in the kitchen with a hot coffee and toast than from inside the belly of the white whale. ( Free study material. )
Mountain Weather	Mountain weather. Invaluable. It's probably easier to learn in the safety of your living room. However, you can also learn a lot about mountain weather by standing on a ridge top while 130 km/h wind sucks the air from your lungs and resurfaces the skin on your face. Yes, afterwards you'll look younger on the outside, but you'll feel older on the inside! ( Free study material. )
Avalanche Forecasting	Avalanche forecasting from Chapter 6 of The Avalanche Handbook. The material is simply amazing and it will help you tie your knowledge together brilliantly. You know what, I'll be honest, it's a tough chapter but it's not certainly not even in the same realm as algebra. It's also not as tough as thinking about how your boyfriend of 15 years will react if someone tells him that you've been killed by an avalanche. ( More free study material. )

My bottom line advice: start out with an AIARE Level 1 class if you're in the US. Check with the CAA if you're in Canada.

Learning About Yourself
This is important on any number of levels, especially if you'd like to get married and stay married. It's also important because learning about yourself teaches you so many things. As with everyone who is approaching 40 as quickly as I am, my personal journey could fill a book or two. Actually, the mistakes alone could fill a book. ( Or maybe two books. But definitely not a library. At least I hope not. )

In all seriousness, I have had my share of moments, including days spent gliding through snow that was hovering right at the razor's edge of serious instability. Gain enough experience and you'll learn what snow feels like when it wants to move. Learn enough about yourself and, unlike me, you'll probably be smart enough to avoid that situation in the first place.

Bottom line: Backcountry avalanche forecasting is much easier when you stop eating idiot sandwiches ( and I ought to know! ). Give introspection and inner peace a chance.

Learning About Snow Metamorphism
I sometimes hear people talk with disdain about the subject of snow metamorphism, especially during conversations about avalanche education. What is snow metamorphism anyway? Well, I have a fairly inclusive definition of snow metamorphism. To me, snow metamorphism starts during crystal formation in the clouds and it ends when the last of the snow melts in the summer. But at any rate, it seems to me that a great many people confuse snow profiles and snowpack tests with snow metamorphism when they're not even remotely the same thing. Snow metamorphism describes how the snowpack forms and understanding the physical properties of snow, including its behaviour from cloud-to-ground, is incredibly useful.

If you don't understand snow metamorphism, then the vague results often associated with snowpack tests aren't very useful. Of course, if you don't understand snow metamorphism, you won't understand why snowpack test results are often vague any more than you'll understand why snow metamorphism is so important in the first place. People who understand snow metamorphism from cloud-to-ground rarely base go/no go decisions on a snow profile. Why is that? It's because they understand the inter-connections between terrain, snowpack, and weather.

Is it important to observe crystals as they fall from the sky? Yes, it certainly can be very important, especially if crystal size increases markedly during a day of powder skiing. This is a sign that a warmer temperature regime is passing over the mountains, and warmer air carries more water vapour. If the day started out cool, an increase in crystal size can indicate the potential for upside down snow. What about poking around in the snow and observing crystal forms? Yes, also important. After all, the snowpack is a living, breathing beast that you must understand if you want to play in the mountains during winter.

Bottom line: Learn about the life cycle of snow.

Learning About Mountain Weather
It's complicated, right? That's putting it lightly indeed. Mountain weather teaches you a lot about snow safety because the unreal complexity of mountain weather—especially the chaotic interaction of weather and terrain—is incredibly humbling. Once you understand the complexity of mountain weather, it's much easier to understand why the snowpack is so complicated. Once you understand the adiabatic lapse rate... well... actually cold air advection is more interesting, but at any rate.

Once you accept the complexity of the interaction between terrain and weather, and its effects on the snowpack, you'll know—I mean you'll really know deep down inside—that it's utterly and stupidly pointless to try and outsmart the snowpack. You'll be forever done with all that pseudo-scientific speculation that always happens during water breaks because you'll understand what you can't know and why you can't know it. Spatial variability won't be a puzzle; it'll simply be what is.

With enough knowledge about, and experience with, mountain weather, it is possible to discern patterns of instability and gain valuable insights about where you shouldn't travel. But here's the thing: having enough knowledge and experience about mountain weather will almost certainly convince you that discretion is the better part of valour.

Bottom line: Mountain weather will amaze and humble you. Learn mountain weather basics for free. Or learn about avalanche weather for free.

Learning About Backcountry Avalanche Forecasting
It's funny how often I answer the same questions. I've even written posts on this blog to answer the same question after it was posed to me by three different people. Last season I received about 100 questions, and most of them were related to backcountry avalanche forecasting. Occasionally the question will involve a dispute between two parties who couldn't agree whether or not they made the right choice for a go/no go decision. Myself, I like to stay out of disputes, so I always decline to answer those questions.

I'm not really sure about the level of knowledge or experience of the people who ask questions, but it is always very clear to me that these nice folks don't have a very good understanding of how backcountry avalanche forecasting works. The questions invariably boil down to the following: I have these observations; what should I do in this situation? As I said above, most recreational backcountry skiers are very skilled at making observations, but far less skilled at prioritising. Prioritising observations is exactly how one minimises uncertainty about instability, and therefore it is at the very heart of backcountry avalanche forecasting.

If you read this blog with any regularity, you are probably well-aware of my near fanatical devotion to The Avalanche Handbook. However, in this case I'm going to make a rare criticism. The chapter on backcountry avalanche forecasting ( called "The ABCs of Backcountry Avalanche Forecasting ) is a confusing mix of weird rules, strange procedures, and useful facts. I didn't really learn anything that I didn't already know, and while I think you should still read the chapter, I've probably read it a dozen times, and it's never made much sense to me. ( I could be stupid! )

Luckily, chapter 6, ( called "The Elements of Applied Avalanche Forecasting" ) is quite brilliant. The authors are quite careful to note that the chapter outlines a theoretical framework for avalanche forecasting, but whatever the case, it just so happens that their theoretical framework is pretty damn excellent.

So, if you want to learn how to integrate observations in order to forecast avalanches, you should study chapter 6, and you should study it hard. I can think of no better learning material. Yes, there are clear differences between office-based forecasting and backcountry avalanche forecasting, but chapter 6 teaches you how to approach the subject with a very professional discipline.

Which certainly won't hurt.

Conclusion
Studying mountain weather, snow metamorphism, and avalanche forecasting will help you develop a detailed mental model of the mountain environment. Studying yourself will help you understand the role your psychology plays in the choices you make. For obvious reasons, it's best to study all the subjects I've discussed here, but I'd choose to learn about myself if I could only pick one.

Sometimes people ask what motivates me to write blog posts and do research ( most of which I do in my spare time, unpaid ). I do this because I know exactly what it feels like to stare death in the face. On a few occasions it might have been my own death, but that never really bothered me all that much. I don't say this because I'm fearless; the truth is that during any such situation I was simply too scared to really think about anything other than getting out.

But it's really scary to stare someone else's death in the face. It's even more awful to feel their death slowly take you down into the darkest places you can imagine. I've been there too, and honestly, few things are worse. This is what motivates me to teach myself.

I guess that's the price of love.

I know it's not cheap.

Perception, Maps, Traps

2011-10-26T17:21:00.000-07:00

I remember, when we could sleep on stones, now we lay together in whispers and moans—U2

I've been working on several projects for the last few years and I wanted to share some output. These findings are related to the statistical model discussed in this post. Rather than a lengthy discussion, I'm simply going to post the images with brief descriptions.

The raster content of these images is used to analyse cells of the terrain for some aspects of exposure to avalanches. Other parts of the statistical modeling rely on data pulled from custom 3D models. This includes variables such as surface area, cumulative slope angle, and terrain trap statistics.

Figure 1.1. Terrain near Paradise, Mount Rainier National Park. The Jackson Visitor Centre is near the upper centre of the image. The Tatoosh range is at the bottom. This image uses natural lighting. Full size image is available here.

Figure 1.2. Terrain near Paradise, Mount Rainier National Park. This image uses slope angle shading. Full size image is available here.

Figure 1.3. Terrain near Paradise, Mount Rainier National Park. This image uses ambient occlusion to determine line-of-sight. Line-of-sight is poorest in the dark areas, but may be relatively poorer in any area that is darker than any other area. This model does not account for trees, and is therefore not easily applicable at the micro-scale. Many dark areas are also terrain traps. Full size image is available here.

Figure 1.4. Terrain near Eldorado, North Cascades National Park. This image uses natural lighting. Full size image is available here.

Figure 1.5. Terrain near Eldorado, North Cascades National Park. This image uses slope angle shading. In addition to making it easy to see slope angles, this image makes it very easy to see areas that are convoluted. Travel is difficult in convoluted terrain, and the skiing is usually pretty bad. Full size image is available here.

Figure 1.6. Terrain near Eldorado, North Cascades National Park. This image uses ambient occlusion to determine line-of-sight. Line-of-sight is poorest in the dark areas. Have you ever looked at a contour map and wondered where you might have route-finding problems? Many dark areas are also terrain traps. Full size image is available here.

Figure 1.7. Terrain near Snoqualmie Pass. This image uses natural lighting. Full size image is available here.

Figure 1.8. Terrain near Snoqualmie Pass. This image uses slope angle shading. In addition to making it easy to see slope angles, this image makes it very easy to see areas that are convoluted. Travel is difficult in convoluted terrain, and the skiing is usually pretty bad. Full size image is available here.

Figure 1.9. Terrain near Snoqualmie Pass. This image uses ambient occlusion to determine line-of-sight. Line-of-sight is poorest in the dark areas. Many dark areas are also terrain traps. Full size image is available here.

Mountain Weather Exam

2011-10-25T16:40:00.000-07:00

225 questions from chapter 2 of The Avalanche Handbook. Questions start with green headings and answers start with red headings. I'm not sure how long it will take to complete this exam, but I can guarantee that you will gain valuable knowledge about mountain weather if you master this material.

This chapter discusses snow formation from cloud to ground, including in-depth information on snow metamorphism and its links to avalanche formation.

Mountain Weather And Snow-Climate Types

Snow layering that contributes to ________ formation is a combination of _______ elements interacting with the _______?
What causes most destructive avalanche cycles?
What primary atmospheric factors contribute to avalanche formation?
What term describes the average weather at any place?
List three snow climates found in North America.
Snow climate is useful for specific elements of avalanche forecasting. True or False?
If snow climate is important, explain why. If snow climate is not important, explain why not.
Snow climate differs by elevation, regardless of geographic location. True or False?
List a key reason why snow climate should not be used to forecast avalanches.

Maritime Snow Climate

List the two key elements of a maritime snow climate.
What type of precipitation can occur at any time during winter in a maritime snow climate?
Snow in maritime snow climates is typically stable. True or False?
Describe the nature of stability or instability in a maritime snow climate.
Describe the rate of change to instability in a maritime snow climate.
List three examples of North American maritime snow climates.
What is the total precipitation ( in millimeters ) for maritime snow climates in North America?
What is the average air temperature, snow depth, and density of new snow for a maritime climate?
Explain the significance.
Avalanche formation in maritime snow climates takes place when?
What is the term for these avalanches?
These avalanches involve snow near the surface? True or False?
What is the term for this type of instability?
List two effects of rain related to avalanche formation.
Persistent structural weakness are common in maritime snow climates. True or False?
If true, explain. If false, explain.
What type of observations are critical for avalanche forecasting in a maritime snow climate?

Continental Snow Climate

List the three key elements of a continental snow climate.
Describe the depth of the snowpack in a continental snow climate.
Snow in continental snow climates is typically stable. True or False?
If true, explain. If false, explain.
Describe the nature of stability or instability in a continental snow climate.
Describe the rate of change to instability in a continental snow climate.
List three examples of North American continental snow climates.
What is the total precipitation ( in millimeters ) for continental snow climates in North America?
What is the average air temperature, snow depth, and density of new snow for a continental climate?
Explain the significance.
Describe the rate of change to instability in a continental snow climate.
Avalanche formation in continental snow climates takes place when?
What is the term for these avalanches?
These avalanches involve snow near the surface? True or False?
What is the term for this type of instability?
What is a distinguishing feature of avalanches in a continental snow climate?
List two weather factors that affect continental snowpacks and how they contribute to avalanche formation.

Transitional Snow Climate

List the two key elements of a transitional snow climate.
Snow in transitional snow climates is typically stable. True or False?
If true, explain. If false, explain.
Describe the nature of stability or instability in a transitional snow climate.
List three examples of North American transitional snow climates.
What is the total precipitation ( in millimeters ) for transitional snow climates in North America?
What is the average air temperature, snow depth, and density of new snow for a transitional climate?
Explain the significance.
Describe the rate of change to instability in a transitional snow climate.
Avalanche formation in transitional snow climates takes place when?
What is the term for these avalanches?

Mountain Wind And Precipitation

Wind ________ and ________ influences precipitation patterns.
Speaking very generally, upon what do those two variables depend?
What is the most important variable for determining wind speed and direction in mountainous terrain.
What is the most important variable for determining the amount and pattern of snowfall in mountainous terrain.
What is the standard atmospheric pressure at sea level? ( In millibars. )
What force slows the wind at the Earth's surface?
At the 700-mb level, what controls wind speed and direction?
Where is free-air found?
Compare differences in airflow at 500-mb to that at the Earth's surface.
Why is this important?
9000m elevation has an approximate air pressure of ________mb.
6000m elevation has an approximate air pressure of ________mb.
3000m elevation has an approximate air pressure of ________mb.
Unlike free air wind speed, ground-based wind-speed sensors provide measurements of air influenced by ________?
Maritime air is warmer than continental air. True or False?
Explain what can happen when a mountain range separates a maritime air mass from a continental air mass.
The vertical component of the wind affects these three components of precipitation.
Rate of precipitation is proportional to ________?
With respect to what you might see in the sky, upward motion of air causes what?
With respect to what you might see in the sky, downward motion of air causes what?
Describe what happens when moisture-laden air is forced up and across mountains.
Provide a definition for the average lapse rate.
Provide a typical value for the average lapse rate.
Cold air is less dense than warm air. True or False?
Explain.
Provide a three word flow chart of what causes precipitation.
What determines the moisture carrying capacity of air before condensation?
This means ________ air carries more water than ________ air.
In simple terms ( two words, an expression familiar to most people ), what might happen if a parcel of warm, moist air is forced over a mountain barrier during winter?
Condensation occurs as water droplets form around what?
The ________ at which air rises, the amount of ________ it contains, and its initial ________ are critical for determining the amount of ________.
Explain two separate scenarios for the above question in general terms and predict the general quantity of precipitation for cold/dry and warm/moist air masses.
List in order of importance the four mechanisms that cause air to rise.
Describe how each mechanism contributes to lifting.
Describe the vertical wind speed, rate of precipitation, duration of precipitation, and horizontal scale for each lifting type.
List the two key mechanisms with respect to winter precipitation.
All these elements act separately. True or False?
Explain.

Air Motion Around Pressure Centers

Define cyclone in simple terms.
Define anticyclone in simple terms.
Describe convergence.
What happens to air as a result?
What happens to the horizontal surface area of the air across the center of a low pressure area?
Why is this important?
Describe divergence.
What happens to air as a result?
What happens to the horizontal surface area of the air across the boundaries of a high pressure area?
Why is this important?

Frontal Lifting

What is a front?
Does lifting always occur over front?
List three types of fronts.
The boundary of a front always slopes ________ over ________ air.
What is the gradient of a typical warm front?
What is the gradient of a typical cold front?
Describe the precipitation intensity and duration associated with each type of front.
Describe the mechanism for lifting that occurs when a warm front passes.
Describe the mechanism for lifting that occurs when a cold front passes.
What influence might a mountain have on warm front lifting?
Why is precipitation more widespread with passage of a warm front than with passage of a cold front?

Orographic Lifting

Describe the process by which orographic lifting occurs.
The vertical component of velocity is a significant fraction of what value?
With respect to air, what is the result of orographic processes?
Why is this important?
Orographic lifting is ________ to ________ times stronger than frontal lifting and convergence.
What is an appropriate range of precipitation totals to expect from orographic lifting.
What terrain factor can increase orographic lifting relative to wind?
What wind factor can increase orographic lifting relative to terrain?
When do maximum orographic effects occur?
Explain.

Convection

Describe the process by which convection occurs.
Convection is a wide area effect. True or False?
In what snow climate and during what season is convection important?

Quantitative Precipitation Forecasts

What information does a quantitative precipitation forecast try to communicate?
Who produces this type of forecast?
What wind variable is the key factor?
Prediction of precipitation amounts is subject to a higher rates of error than wind and temperature. True or False?
Precipitation amounts are normally forecast at what scale?
What is the size of this scale?
Avalanche forecasting requires quantification of precipitation at what scale?
What is the size of this scale?
What is the primary model used by avalanche forecasters to predict precipitation for mountainous terrain?
Explain why this model is chosen relative to the size of the synoptic, meso, and micro scales.

Orographic Precipitation Models

What is the key assumption of an orographic precipitation model?
An air mass forms over the ocean and moves west across three mountain ranges. Describe each snow climate and amounts and expected quantity ( in general terms ) of precipitation.
Why does precipitation increase or decrease when an air mass crosses three mountain ranges?
Name two or three key data items required by an orographic precipitation model?
How are these data acquired?
How is duration of precipitation forecast?
Describe the three key local effects with respect to mountain-precipitation forecasting.
Why might snowfall increase at higher elevations?
Why might snowfall decrease at lower elevations?

Local Wind Flow Over Mountain Terrain

Wind ________ and ________ are considered essential inputs for modern forecasting.
Describe the most important reason why local wind speed and direction is important for backcountry travel.
Relative to terrain, why does wind speed generally increase with height?
Snowfall is generally greater on which side of a mountain?
List two reasons why.
Snow is ________ where wind ________.
Snow is ________ where wind ________.
What causes acceleration of wind?
Describe wind flow quality during acceleration?
Describe wind flow quality during deceleration?
Describe a terrain feature that increases turbulence.
With respect to wind direction, describe one effect of turbulence associated specifically with deceleration on the leeward side of a ridges.
What is the result?
Minor changes in slope angle have a significant affect on the character and areal distribution of wind deposited snow. True or False?
Describe a wind effect that might produce cross-loading.
What conditions are necessary to form a foehn / chinook wind?
What is the main feature of a foehn wind?
What snowpack element might be formed during passage of a foehn wind?

Blowing And Drifting Snow

Can avalanches occur from loading when snow is not falling from the clouds?
If so, explain. If not, explain.
What is threshold wind speed?
List three factors ( weather or snow ) that affect threshold wind speed.
What is threshold wind speed for loose snow?
What is threshold wind speed for bonded snow?
What are the three modes of transport for wind-redistributed snow?
________ occurs at what height?
________ occurs at what height?
________ occurs at what height?
The majority of snow transport occurs at what height?
What often happens to snow particle size during wind transport?
Describe the importance or unimportance of any changes to snow particle size that occur as a result of wind transport.
What is an obvious sign of wind drifting on an otherwise clear day?
Describe snow distribution in the mountains.
List three terrain elements that influence snow distribution.
How might snow distribution during winter affect wind-deposition?
What is the minimum change-of-slope angle necessary to alter development of snow drifts?
Why is this important?

Lee Slope Deposition

Where are cornices often found?
How do cornices form?
What snowpack element is often found below a cornice?
Is this snowpack element important?
Describe the density of snow found in cornices.
List a reason why this might be important.
List three important features of cornices with respect to avalanche formation.

Heat Exchange At The Snow Surface

List three methods by which heat exchange occurs at the snow surface.
Describe each method.
Describe one possible effect of heat exchange at the snow surface.
How might new snowfall warm or cool the snow surface?
What might happen when a temperature difference exists between the snow surface and new precipitation?

Penetration Of Heat Into Alpine Snow

List the two primary mechanisms by which heat is transferred within snowpack.
Describe each.
What is the primary heat transfer mechanism in low density snow?
What is the primary heat transfer mechanism in high density snow?
Heat transfer through low density snow is more or less efficient as temperature decreases?
Why is this important?
Heat transfer in alpine snow is very rapid. True or False?
Why is heat transfer important?

Interaction Of Radiation With The Snow Cover

List the two key types of radiation that affect snow surface temperature.
What is the source of each?
Does radiation deeply penetrate the snowpack?
In general, how much shortwave radiation is reflected by dry snow and wet snow?
For fresh, fine-grained snow, how much solar radiation remains after 10 centimeters of depth?
Solar radiation can heat or cool the snowpack. True or False?
Which matters more, type of radiation or balance of radiation.
Explain.
Describe what happens to a south facing slope on a clear day during mid-winter.
Describe what happens to a north facing slope on a clear day during mid-winter.
With respect to radiation, what might happen during a clear night?
With respect to radiation, what might happen during a cloudy day?
Why is long wave radiation loss important?

Temperature Inversions

Describe a temperature inversion.
What is the typical cause of a temperature inversion?
Under what circumstances might a temperature inversion be important?

Mountain Weather And Snow-Climate Types

Snow layering that contributes to avalanche formation is a combination of weather elements interacting with the snowpack?
Direct loading of snow from synoptic scale weather events.
Precipitation patterns and intensity, wind direction and speed, sensible heat, and radiational heating and cooling of the snow.
Climate
Maritime, Transitional, Continental
False.
Not Important. Avalanche prediction is dynamic and highly time-dependent, regardless of snow climate.
True
Any snow climate may have some characteristics of other snow climates.

Maritime Snow Climate

Warm temperatures and heavy snowfall.
Rain
True
Changes to instability are rapid and frequent.
Coast Range ( British Columbia ), Cascade Range ( Washington State), Sierra Nevada ( California ).
1280 millimeters
-1.3 degrees Celsius, 190 centimeters, 120 kilograms / cubic meter.
Deep snowpacks are better insulated against environmental effects. High temperatures quickly reduce instability in new snow and reduce magnitude of temperature gradient.
During and immediately after storms.
Direct-action avalanches.
True
Temporary instability, surface instability, new snow instability, storm snow instability.
Heavy rain loads the snow and can contribute to formation of ice crusts.
False
Warmer temperatures and deeper snowpacks promote metamorphism and bond formation by heat and overburden.
Weather Observations

Continental Snow Climate

Low snowfall, cold temperatures, location considerably inland from coastal areas.
Shallow
False
Snowpack in continental climates is typically unstable because of structural weaknesses induced by shallow snowpacks and cold temperatures.
Mostly persistent instabilities, new snow instabilities are secondary.
Instability is slow to change because of cold temperatures and often persists through entire season.
Brooks Range ( Alaska ), Canadian Rockies, American Rockies.
550 millimeters
-7.3 degrees Celsius, 110 centimeters, 70 kilograms / cubic meter.
This produces a shallow snowpack subject to environmental effects. Cold temperatures help instability form and persist.
Slow. Instability persists for long periods, often for entire season.
Avalanches occur at all times but often in nice weather long after a storm passes.
Delayed action avalanches.
False
Persistent instability, deep instability.
Avalanches tend to involve old layers of snow.
Low snowfall leads to thin snowpacks. Cold temperatures create large magnitude temperature gradients that weaken the snowpack. Clear air drifting loads slopes.

Transitional Snow Climate

High snowfall and cool temperatures.
True
While snow in transitional climate is often stable, transitional snow climates are subject to frequent new snow instabilities and persistent instabilities buried in the snowpack.
New snow instability, some persistent instability.
Columbia Mountains ( British Columbia ), Wasatch Mountains ( Utah ), Madison Range ( Montana )
850 millimeters
-4.7 degrees Celsius, 170 centimeters, 90 kilograms / cubic meter.
Lots of snow and deep snowpacks provide some insulation against environment effects. However, cooler temperatures allow deep instabilities to persist. In general, snowpack is stronger than continental but may be weaker in places than maritime.
Slow to change in the early season, quick to change later in the season. New snow instabilities vanish relatively quickly; persistent instabilities often last entire season.
During storms, after storms, and long after storms.
Direct action and delayed action avalanches.

Mountain Wind And Precipitation

Wind speed and direction influences precipitation patterns.
Wind speed and direction depend on the balance of forces in the atmosphere.
Horizontal component of wind velocity.
Vertical component of wind velocity.
1013 ( 1000 is acceptable. )
Friction
Atmospheric pressure differences, frictional forces, and Coriolis force.
Free air wind is located several hundred meters above rough mountain topography.
Air flow at 500-mb is parallel to pressure contours. Airflow at the Earth's surface blows across pressure contours.
In high mountain terrain, wind blows toward lower pressure. This must be understood if you wish to predict wind direction and speed.
9000m elevation has an approximate air pressure of 300 mb.
6000m elevation has an approximate air pressure of 500 mb.
3000m elevation has an approximate air pressure of 700 mb.
Friction induced by air motion across rough terrain features.
True
Free air winds might blow in the opposite direction of surface pressure winds.
Quantity, rate, and duration.
The vertical component of wind velocity.
Cloud formation and precipitation.
Cloud dissipation and clearing.
Temperature decreases with height due to expansion of the air mass. The air mass cools as it expands, leading to condensation and cloud formation. Precipitation occurs when the air cannot hold moisture because of temperature decreases.
Reduction in air temperature with increasing altitude.
1 degree Celsius / 100 meters or 6.5 degrees Celsius per 1,000 meters.
False
Cold air is denser than warmer air. This is why it has higher pressure.
Lifting, expansion, condensation; rising, cooling, condensation; any three correct terms are acceptable.
Temperature
This means warmer air carries more water than cooler air.
Snow storm.
Condensation nuclei.
The rate at which air rises, the amount of moisture it contains, and its initial temperature are critical for determining the amount of precipitation.
Cold, dry air does not rise; no precipitation is the result. Warm, moist air rises quickly; heavy precipitation is the result.
Orographic lifting, frontal lifting, convergence, convection.
Description of lifting mechanisms:
- Orographic. This mechanism involves motion of air across mountains with lifting occurring as a result of wind intersecting with mountain barriers and steep terrain.
- Frontal. This mechanism involves motion of warm air rising over cold air or cold air displacing warm air, resulting in lifting.
- Convergence. This mechanism involves air moving toward a low pressure area and being lifted through displacement.
- Convective. This mechanism involves lifting that occurs when air is warmed at the Earth's surface.
Description of lifting parameters:
- Orographic. ~1 centimeter / second - 2 meters / second, 1-5 millimeters per hour, up to tens of hours, 10-100 kilometers.
- Frontal. ~1 centimeter / second - 20 centimeters / second, ~1-10 millimeters per hour, up to tens of hours, 100 kilometers for width and 1000 kilometers for length.
- Convergence. ~1 centimeter / second - 10 centimeters / second, up to 2 millimeters per hour, tens of hours to several days, 1000 kilometers.
- Convective. ~1 centimeter / second - 10 centimeters / second, ~1-30 millimeters per hour, minutes to hours, 0.1 to 10 kilometers.
Orograph lifting, frontal lifting.
True
Most of these mechanisms operate at the same time but orographic and frontal lifting have the strongest effect and therefore are the key factors for mountain precipitation.

Air Motion Around Pressure Centers

A low pressure center.
A high pressure center.
Convergence involves air motion toward a low pressure center. As air moves toward the low pressure center, existing air is displaced upward ( lifted ).
Lifting.
The horizontal surface area decreases. This causes displacement as air is drawn inward. Lifting is the result.
This results in cloud formation over a large area and widespread precipitation over any mountainous terrain near the low pressure center.
Divergence involves air motion outward from a high pressure center. As air moves outward, it sinks, causing clearing.
The air sinks.
It increases.
This results in clearing over any mountainous terrain near the high pressure center.

Frontal Lifting

A boundary between two air masses.
Yes.
Warm, Cold, Occluded, Stationary
The boundary of a front always slopes warm over cold air.
1:100
1:25
Description of precipitation intensity:
- Warm Front. Steady, long-lasting ( up to 18 hours or more ), widespread across front.
- Cold Front. Intense, short ( 4-6 hours ), oriented parallel to front.
Warm air rises up over the cold air.
Cold air flows underneath the warm air, displacing the warmer air and forcing it upward.
Mountains increase lifting associated with a warm front.
Slope differences. A warm front has a gradient of 1:100; a cold front has a gradient of 1:25. Therefore a cold front is narrow and a warm front is wide.

Orographic Lifting

Orographic lifting occurs when air is forced over mountain barrier. Up is the only possible direction of motion.
Horizontal wind speed.
Lifting
Lifting results in expansion and cooling. Cloud formation and precipitation follow soon thereafter.
Orographic lifting is 10 to 100 times stronger than frontal lifting and convergence.
50-70%
Steepness of terrain.
Directness of wind strike angle
When strong wind blows perpendicular to steep terrain.
Wind blowing perpendicular to steep terrain is expected to produce the most vertical velocity and therefore the most lifting.

Convection

Convection occurs when air is warmed near the Earth's surface.
False
Convection is important during summer in continental snow climates.

Quantitative Precipitation Forecasts

Forecast the quantity of precipitation. Quantity = quantitative.
Avalanche forecasters, mountain weather forecasters.
Vertical component of wind velocity.
True.
Synoptic
1000km
Meso or micro.
1-100km
Orographic Precipitation Model
Orographic precipitation models work at the meso and micro scale. Synoptic scale predictions are too vague for meso-scale forecasting.

Orographic Precipitation Models

Precipitation is produced at a rate that is directly proportional to the rate at which air is being lifted.
Maritime, Transitional, Continental. Very High Quantity, High Quantity, Low Quantity.
Precipitation decreases because each mountain range results in a storm that decreases the amount of moisture in the air mass.
Wind speed, wind direction, moisture content, air temperature, lapse rate, thickness and width of air mass.
From upper air soundings and standard forecast products.
By estimating width of the moist layer and wind speed
Topographic Convergence, Orographic Convergence, Valley Channeling
Orographic effects enhance precipitation at higher elevations.
Slow moving air mass, in conjunction with low freezing levels, produces most of its precipitation at lower elevations.

Local Wind Flow Over Mountain Terrain

Wind speed and direction are considered essential inputs for modern forecasting.
To determine if/when/where wind loading might occur.
Orographic effects.
Windward
Lifting is highest on windward side and a lot of precipitation occurs as a result, leaving less moisture available for precipitation on the lee side.
Snow is lifted where wind accelerates.
Snow is deposited where wind decelerates.
Vertical compression of air.
Laminar, Smooth, Connected
Turbulent, Separated, Reversed
Sharp ridges.
Reversal of flow.
Cornice formation.
True
Valley/Canyon Wind, wind across slopes
Large-scale, low-pressure area in the lee side of mountain range.
Intense, warm flow.
A crust.

Blowing And Drifting Snow

Yes
Wind can transport snow. This causes heavy loading on already unstable slopes or heavy loading that destabilizes a previous stable slope.
The wind speed required to create blowing snow for a given set of conditions.
Humidity, temperature, density, time since deposition.
5 meters / second
25 meters / second
Rolling, Saltation, Turbulent Suspension
Rolling occurs between 0-1 millimeters.
Saltation occurs between 1-10 centimeters.
Turbulent suspension occurs between 10-100 meters.
The lowest meter above the surface.
The particles are shattered into tiny fragments.
This is important because it leads to formation of dense, heavy wind slab, often on already unstable slopes.
Blowing snow visible at any location.
Uneven, chaotic, variable.
Gullies, ridges, vegetation, cols, notches, gully walls.
As small features are filled in with snow, more snow is available for distribution elsewhere.
10 degrees.
Safe travel requires the ability to assess the influence small scale features have on avalanche formation.

Lee Slope Deposition

Ridges
Wind flow becomes turbulent during deceleration. This causes reversal of flow and vortex formation.
Wind slab.
Yes, wind slab is often loaded onto already unstable slopes.
Very high, up to 500kg / cubic meter.
Heavy cornices make great avalanche triggers.
Cornices provide a method to assess wind direction, steep lee area below cornice is prime real estate for unstable slabs, collapse of cornice leads to avalanches or injuries.

Heat Exchange At The Snow Surface

Convection, Conduction, Radiation
Description of each method:
- Convection. Heat is transferred through air.
- Conduction. Heat is transferred through bonds between existing ice particles or between existing ice particles and new snow.
- Radiation. Heat is transferred through incoming or outgoing radiation.
Weakening of snow surface. Crust formation.
Colder snow on warmer surface, warmer snow on a colder surface.
Poor bonding because of temperature mismatch.

Penetration Of Heat Into Alpine Snow

Vapor diffusion through air space in pores or conduction through individual ice bonds.
Description of each:
- Vapor Diffusion. Water vapor moves through the pore space from warmer areas to cooler areas, resulting in heat transfer.
- Ice Bonds. This occurs when heat moves from warmer snow to cooler snow through connections made by ice bonds.
Vapor diffusion through the pore space.
Conduction through ice bonds.
Less Efficient
This proves vapor diffusion is responsible for heat transport through low density snow.
False
Heat transfer is the primary mechanism that controls metamorphism ( via temperature gradient ).

Interaction Of Radiation With The Snow Cover

Short wave and long wave radiation.
Short wave = sunlight. Long wave = terrestrial sources such as stored heat, water vapor, carbon dioxide.
No.
Dry snow = 90%, Wet snow = 80%.
Less than 10%
False. It can only heat the snowpack.
The balance of radiation.
The balance of short wave and long wave radiation controls heating and cooling of the snowpack and certain balances of radiation can produce a weak snowpack, i.e. lots of solar radiation input during the and long wave radiation loss at night.
The snowpack warms up.
The snowpack cools.
Intense cooling through loss of long wave radiation into outer space.
A greenhouse effect might trap short wave and long wave radiation and warm the snow, inducing instability.
Long wave radiation loss can create a strong temperature gradient, resulting in development/growth of facets, surface hoar, or crusts.

Temperature Inversions

Temperature rises with elevation.
Long wave radiation loss results in cooling of the snow at high elevations. This produces cold air that sinks into the valley below.
A temperature inversion might result in reservoirs of cold air on one side of a mountain range. Passage of a warm front over this cold air might cause rain in avalanche starting zones.

Interesting

2011-09-19T01:23:00.000-07:00

There is always the promise of an early winter. To that end, I recently ran across a fascinating article about intuitive thinking, and I wanted to share it. It's a must read for anyone who deals snow ( or people ).

http://edge.org/conversation/the-marvels-and-flaws-of-intuitive-thinking&from=admin

Happy Trails!

2011-05-03T21:28:00.000-07:00

Well it's about that time of year. Time for me to go off on some big spring ski trips, and time to put the blog on hiatus for the summer. Thanks for reading again this year, and I wish everyone a safe, happy summer. Expect new posts again at the start of November.

Best,

CookieMonster

Be Fucking Careful!

2011-03-08T02:27:00.000-08:00

If you live in Washington State, now is a very good time to be very fucking careful. There have been a rash of incidents over the last week, and there are signs of deep instability lurking below the winter snowpack in some areas.

Avalanche Kills Leavenworth Man
Close call on the Funnelater ( which is a fun line in stable conditions ).
Buried Monsters Near Crystal Mountain

Deep instabilities are not typically found in the maritime snowpack we have here Washington State; this means that terrain that is usually safe might be very dangerous. Now is a good time for snowpack observations. To this point, the report from Crystal Mountain cited a Q1 shear at 48" below surface. The fracture was described as "like a filing cabinet", which implies a clean, rapid failure.

This is a crystal clear sign of snowpack instability.

It is not possible to manage the risk associated with deep instabilities due to wide variances in snowpack structure and the associated fluctuations in the energy required for avalanche formation. Deep avalanches are always large and unsurvivable.

As always, make decisions that strike a balance between awareness and uncertainty.

Just For Fun

2011-02-24T21:21:00.001-08:00

The Scientific Method

2011-02-23T10:11:00.000-08:00

It's been a slow winter here in Washington, with a lot of rain, and not a lot of snow. This means that avalanche danger has been low for a long time, and it's easy to get out of the avalanche safety habit, especially if your avalanche safety habits are inconsistent in the first place.

What forms the basis of our avalanche safety habits?

On Monday I skiied Chair Peak with two local characters. Had an incredibly fun day out and about in the snow. At one point during the day, one of my ski partners asked me if I had ever thought about teaching avalanche education courses. Yes, I've thought about it. But, unfortunately, while I am allegedly qualified to teach avalanche courses, I don't have enough free time.

But it got me thinking. What would I even teach?

I would teach the scientific method, because it's what I use, and based on my current understanding of avalanche safety, the scientific method is the only realistic approach. But I wouldn't start by assuming that my students couldn't learn. Avalanche safety is a blend of complex sciences, and yes, there is a lot of complicated material. That said, learning how to approach the challenge of avalanche safety is the single most important thing you can ever learn about avalanche safety.

The scientific method provides a fantastically simple framework for teaching avalanche safety, and the primary observation categories are already determined: terrain, weather, snowpack, and humans. You start out with nothing and gradually collect information. This information helps you form inferences that eventually lead you to a conclusion. These conclusions tell you where and when to travel. Yes, as with all forms of science, it is incredibly important to avoid bias.

It really comes down to learning how to conduct observations that tell you whether or not it's safe to travel at a specific time and place. The where and when of it, if you will. The Avalanche Handbook clearly states that applying the scientific method is a good first step. If I taught avalanche classes, I wouldn't tell my students that avalanche safety is complicated and difficult, I would tell them that avalanche safety involves learning how to apply the scientific method to the problem. In short, the scientific method of avalanche safety involves observations, inferences, and conclusions that help us decide.

Avalanche safety is all about where and when can I travel based on the available data? Much of what we refer to as safety rituals or good habits really refers to the consistency with which we apply the scientific method to the problem. All the huzz about human factors just refers to the avoidance of bias in order to ensure that what we do is actually science.

Scientists have to avoid bias or their work isn't scientific. I know how this feels, because there have been days when I've stared at data on my computer screen, wishing that I could find a way for the data to provide the conclusion that I wanted it to provide.

The problem is that wishes and wants aren't science, and in the backcountry, they'll get you killed.

Further Reading:

The Scientific Method ( You won't get very far before the subject of human factors is raised. )
Elements of Backcountry Avalanche Forecasting ( A blog post I wrote in late 2009. )
The Science Behind Wind Loading
The Science Behind Snowpack Observations
The Science Behind Terrain Observations
The Science Behind Weather Observations
The Science Behind Human Observations
The Science Behind Perception of Instability

Addendum
The following is an excerpt from my contribution to an article in The Avalanche Review. This article discussed the relationship between large avalanche cycles and backcountry avalanche forecasting. You'll see that the discussion is centred around the scientific answer to the question how does an avalanche cycle change instability in the short, medium, and long-term.

The size of the forecast region is the most important factor, with precise answers only available for very small areas. However, even for small areas, the chaotic interaction between terrain and weather makes it difficult to predict the effects of widespread avalanching on future snowpack instability. The following scenario, which is just one possibility out of many, hints at the overall complexity of this forecasting problem.

Instability will persist when a bed surface composed of faceted crystals is immediately reloaded during a storm. On the other hand, future snowpack instability on that slope will be very different if the faceted crystals exposed by avalanching are subjected to multiple melt/freeze cycles prior to the next storm. Melt/freeze activity is often limited by aspect, so it is possible for the faceting process to continue on cold aspects, while faceted crystals on warm aspects undergo rounding as a result of melt/freeze metamorphism. In this highly general scenario, the weather builds new patterns of snowpack instability that are difficult to uncover without careful observations.

Therefore, for most recreational skiers, knowledge of a recent avalanche cycle is a very general and imprecise piece of information. General information often has a dangerous and unwarranted influence on individual or group beliefs about the presence of instability and its parameters. Without abundant information, expert knowledge, and significant experience ( Randy and Nick provide great examples ), a recent avalanche cycle should not exert undue influence on recreational travel choices and decision-making at any operational scale. More than anything, incremental changes to the snowpack caused by synoptic scale weather events will alter the characteristics of the danger but won't eliminate it.

The chaotic relationship between terrain and weather is a primary source of uncertainty.
Incremental changes to the snowpack are a primary source of uncertainty.
Avalanches remove weak snow from some, but not all, slopes.
Avalanches may or may not remove all the weak snow from a specific slope.
Use multiple sources of information to determine the likelihood of avalanche formation.
An avalanche cycle over a large area certainly does not mean a specific slope is safe.

Proactively managing uncertainty is essential to safe decisions.

Cut On the Bias

2011-01-26T15:56:00.000-08:00

When it comes to decisions, avalanche education often centres itself around biases. ( Referred to as human factors. ) Here is some very high-end thinking on biases from Oxford University.

Feeling Rational: http://lesswrong.com/lw/hp/feeling_rational/
The Role of Bias in Bias: http://lesswrong.com/lw/he/knowing_about_biases_can_hurt_people/
The Affect Heuristic: http://lesswrong.com/lw/lg/the_affect_heuristic/

Might make your brain hurt a bit, but that's a good thing, right?

Q & A

2011-01-14T13:11:00.000-08:00

Answers to questions sent to me via email.

Why is buried surface hoar so dangerous?
Buried surface hoar is dangerous because surface hoar crystals form a thin layer that contains a lot of air. This means that the layer on top of the surface hoar is mostly supported by air. When crushed, surface hoar crystals have the capacity to rearrange themselves into a much smaller space, which causes the layer above to fall. As the layer falls, it provides energy that causes the crushing to spread. After the crushing process is complete, you're left with two layers of snow that have no attachment to each other-delamination has occurred. Finally, gravity, which is always in effect, pulls the detached layer downhill.

All the persistent forms ( facets, depth hoar, surface hoar, and combinations of these with crusts ) are dangerous for this reason. Crusts, when found alone, are dangerous for slightly different reasons, mostly related to poor bonding at the interface between the crust and the layer above-poor bonding increases the risk of catastrophic delamination, and catastrophic delamination is required for avalanche formation. The answer provided here intentionally does not discuss weak layer parameters such as anisotropy or variations in grain morphology, which are more related to why the layers are persistent than to why they are dangerous.

What is the significance of snow crystal size?
There are two key factors related to crystal size: the first factor is that large crystals have a lower number of bonds per unit volume. This is part of the reason why the persistent forms, such as facets and surface hoar, are so weak. Networks of large crystals can be quite strong, but they are almost always relatively weaker than networks of smaller crystals.

The second factor is grain size mismatch between layers. Grain size mismatches result in weaker bonding between layers, because the smaller grains overlay the pore space between the larger grains. This means a lot of the smaller grains are simply "touching the air". Furthermore, such configurations tend to concentrate stress at the interface between the layers.

What wind speed produces wind slab?
This depends almost entirely on the condition of surface snow. It takes little more than a stiff breeze to move dry, loosely packed snow. On the other hand, hurricane force winds will have little effect on dense, frozen corn snow.

What is the source of uncertainty in persistent weak layers?
With respect to persistent weak layers, uncertainty arises from a few key factors:

Where is the weak layer?
What is its depth below the surface?
How weak is the layer and surrounding interfaces?

Picture a mountain valley. You know that there is buried surface hoar in some places. You also know that its depth below the surface varies. You also know that its degree of weakness varies by location.

Now that we've discussed what you know, think about what you don't know.

Snowpack Synopsis for British Columbia Interior Ranges

2011-01-08T12:33:00.001-08:00

A great read from James Floyer.

http://www.avalanche.ca/cac/library/researchandarticles/2011-01-06_Snowpack_Synopsis

Enjoy!

Forecasting 101

2011-01-04T18:57:00.000-08:00

if I knew then, what I know now—from the vernacular

There are lots of options for improving your avalanche forecasting skills, but what happens after you've taken an avalanche safety training course? The idea is to get out and gain experience, but the relationship between experience and skill is tenuous. Yes, you need to get out and ski tour, but you also need to focus on increasing your skill, so that all your hard-earned experience doesn't go to waste.

I get a few emails each month in which people ask me how to break past a learning plateau, and my answer is, increasingly, to engage in some self-directed study. Of course, the question then becomes what should I study?

When I think about all things I've learned about avalanches, several things really stick out as useful. Snow metamorphism is one of the most useful topical areas, and of course, learning the best practises of risk management is also really useful. You should also study avalanche formation because the information you learn is incredibly useful when interpreting snowpack test results. Of course, all this leads in the general direction of improving your backcountry avalanche forecasting skills, and there is one resource that is utterly peerless in this regard.

Chapter six of The Avalanche Handbook lays out a theoretical framework for avalanche forecasting that I've found very useful. The elements of applied avalanche forecasting are as follows:

Definition. Forecast snowpack instability across space and time.
Goal. Align your perception of instability with reality.
Information Types & Relation To Perception. The relationship between instability and Class III, II, and I factors.
Scales in Space and Time. Considering avalanche forecasting in terms of spatial and temporal parameters.
Human Factors and Perception. Managing your state of mind and remaining objective.
Reasoning Processes. Learn how to apply inductive and deductive reasoning to the problem.
Decision-Making. How to manage risk.

When I first read this chapter, my mind certainly did a few backflips and double-takes. How do you take something this complex and apply it in the real-world? After a few more reads, and after some directed study of the material, including extensive Q & A, I finally was able to wrap my brain around the concepts.

I'm prepared to make a fairly steep claim in this post, and it is as follows: there is no better way to learn how to forecast avalanches than to study the material in this chapter until you know it forwards and backwards. Naturally, I've prepared an exam that you can use to gauge your progression.

Elements of Avalanche Forecasting Exam

2011-01-01T18:50:00.000-08:00

124 questions from chapter 6 of The Avalanche Handbook. As with my other exams: Yes, I am fully aware that this exam is ridiculous, but it was a lot of work, so have fun.

Capsule

This chapter discusses avalanche forecasting. The seven elements of avalanche forecasting are discussed, as well as the basis for each. The elements of forecasting are linked through risk concepts ( especially perception / perceptual errors related to data sampling ) to form a framework suitable for learning basic forecasting. Specific forecasting techniques and procedures are not included because, given the multitude of forecasting contexts and the dynamic, evolutionary nature of the forecasting process, there is not really a specific process used to issue a forecast. At the end of this chapter you should understand the basis for avalanche forecasting, data types, human perception, and the links between these forecast components and risk concepts such as error, probability, and decision-making.

List Of Sections

Forecasting And Avalanche Forecasting.
This section contains a detailed overview of forecasting, avalanche forecasting,
and including relevant details on methods and pitfalls.
The Seven Elements Of Avalanche Forecasting.
This section contains in-depth analysis of each element of avalanche forecasting.
Common Biases And Decision Traps In Avalanche Forecasting.
This section contains an in-depth explanation of biases and decision traps, along
with techniques to neutralize these biases and avoid decision traps.

Forecasting And Avalanche Forecasting

Around what element is modern avalanche forecasting framed? From what perspective are forecasts issued?
List all seven elements of applied avalanche forecasting.
Avalanche forecasting is a ________ problem.
All seven elements are ________.
Most avalanche accidents occur as a result of human errors. True or False.
Provide the definition of forecasting.
Define the root cause of most avalanche accidents.
How is avalanche forecasting linked to risk analysis?
Is avalanche forecasting limited only to estimates of instability? Explain why or why not.

I. Definition Of Avalanche Forecasting

Define avalanche forecasting.
Define the major physical uncertainty with respect to avalanche forecasting.
Avalanche forecasting is defined in terms of ________.
Whereas traditionally, avalanche forecasting was defined in terms of ________.
In avalanche forecasting, what type of information is most highly prized?
To what does triggering level refer?
Provide three examples of types of forecasting relative to triggers.
How do most slab avalanches release?
Some avalanches release without the need for an external trigger. True or False.
If true, explain. If false, explain.
Upon what does the energy required to release a slab avalanche depend?
What is the primary reason avalanche forecasting is probabilistic, with a risk-based character?

II. Goal Of Avalanche Forecasting

Define the goal of avalanche forecasting. Discuss the primary sources of uncertainty.
State the goal of avalanche forecasting from the human perspective.
How is this goal accomplished?
Define relevant information in the context of avalanche forecasting.
There is a strong link between quantity of information and accuracy of decisions. True or False.
There is a strong link between confidence in a decision and the resulting accuracy. True or False.
Briefly discuss the role of redundant information in statistical predictions.
List and describe each data classification.
Discuss ensemble forecasts.

III. Human Factors And Perception

Discuss the scale of failure in human perception with respect to avalanches.
Define perception.
Discuss the two general components of human influences.
Connect risk-taking propensity to perception.
What relationships does the Risk-Decision Matrix display?
Define Operational Risk Band [ ORB ].
What is the upper boundary of the ORB?
What is the lower boundary of the ORB?
Provide a list of Type I errors.
Provide a list of Type II errors.
Define target risk.
What are the consequences of Type I errors.
What are the consequences of Type II errors.
What is the relationship between uncertainty and perception?
Who coined the term risk homeostasis?
Explain risk homeostasis and provide an example.
List two or three items that improve perception.
List two or three items that degrade perception.
When might biases have a small effect on perception of instability?
When might biases have a large effect on perception of instability?
Discuss absolute instability relative to perception.
Discuss conditional instability relative to perception.
Write a brief explanation of the implications of perception of instability and the public danger scale.
Draw the continuum of instability and describe perception at three points.
Why is the link between data sampling and perception so important?
What does White ( 1974 ) argue about perception of hazard?
What is shown by statistics that compare fatalities to the public danger scale?
Why is perception better for instability in new snow?
Is randomness desired in the sampling process for avalanche forecasting?
Why are slopeside stability tests sometimes compared to playing the lottery?

IV. Reasoning Processes

Define the two main types of reasoning used in avalanche forecasting.
Provide an example of each type of reasoning.
Snow stability is dynamic and evolutionary, therefore avalanche forecasting is ________ and evolutionary.
What underpins the dynamic nature of avalanche forecasting?
The dynamic process of ________ ________ about instability using ________ ________ is somewhat analogous to ________ ________ using ________ ________ as ________ ________.
For a given avalanche path, when does the ideal forecast period begin?
Explain the answer to the previous question, in the context of forecast revision.
Define Bayes Theorem.
In avalanche forecasting, relative to Bayes Theorem, what constitutes the prior?
In avalanche forecasting, relative to Bayes Theorem, what constitutes the likelihood?
In avalanche forecasting, relative to Bayes Theorem, what constitutes the posterior?
Discuss the relationship between inductive reasoning, datums, and forecast revisions relative to instability.
How does an avalanche atlas fit into the context of avalanche forecasting as a Bayesian process?
In the context of avalanche forecasting, instability is not highly time-dependent. True or False.
If this is false, explain why.
List three examples of the deductive elements of avalanche forecasting.
Compare the evolutionary character of reasoning for helicopter backcountry skiing and ordinary backcountry skiing.

V. Information Types And Relation To Perception

Information for avalanche forecasting consists of two types. Explain each and include examples.
Should one always have an opinion about instability before attempting risky activities in avalanche terrain?
Describe the correct course of action if information relevant to the case at hand is missing at the beginning of a forecast period.
Describe a method to implement the correct course of action for the previous question.
If avalanche forecasting is Bayesian, what information type constitutes the likelihood?
If avalanche forecasting is Bayesian, what information type constitutes the prior?
Can data derived from computer models constitute the prior?
Define informational entropy.
Why is wind speed and direct data harder to interpret than cracking of the snow cover?
Define highly correlated.
What is necessary for dealing with highly correlated data?
Does the class of information ( I, II, III ) always give the most priority to Class I information?
Describe the theory of weighting data.

VI. Scales In Space And Time

Define spatial scale relative to avalanche forecasting.
Define temporal scale relative to avalanche forecasting.
Define scale-matching.
Provide an example of what might happen if scale-matching is not performed.
Explain the three primary spatial scales.
Difficulty of forecasting is inversely proportional to scale. True or False.
If true, explain. If false, explain.
Does failure to perform scale-matching result in many needless accidents?
Define now-cast.
Which is more difficult: forecasting stability for next Wednesday or next Thursday?
Why does chaos influence avalanche forecasting?

VI. Decision-Making

Provide a basic list of steps used to issue an avalanche forecast.
Why formalize the decision-making process?
Relative to avalanche forecasting, what underpins the fundamental residual risk with all decisions?

Conclusions

Why is a chain of events difficult to construct for avalanche forecasting?
Where do terrain and snow climate fit into the avalanche forecasting?

Biases

Discuss "search for supportive evidence" and how to neutralize this bias.
Discuss "inconsistency" and how to neutralize this bias.
Discuss "conservatism" and how to neutralize this bias.
Discuss "recency" and how to neutralize this bias.
Discuss "frequency" and how to neutralize this bias.
Discuss "availability" and how to neutralize this bias.
Discuss "illusory correlations" and how to neutralize this bias.
Discuss "selective perception" and how to neutralize this bias.
Discuss "expert halo" and how to neutralize this bias.
Discuss "underestimating uncertainty" and how to neutralize this bias.
Discuss "excessive optimism" and how to neutralize this bias.
Discuss "anchoring" and how to neutralize this bias.
Discuss "rules of thumb" and how to neutralize this bias.
Discuss "guide-client relationship" and how to neutralize this bias.
Discuss "social proof" and how to neutralize this bias.

Chapter 6 Exam Answers

245 answers to questions from chapter 6 of The Avalanche Handbook.

Forecasting And Avalanche Forecasting

Modern avalanche forecasting framed around instability and conducted from the perspective of the trigger.
The seven elements of applied avalanche forecasting are as follows:
- Definition
- Goal
- Human Factors And Perception
- Reasoning Processes
- Information Types & Relation To Perception
- Scales Of Space And Time
- Decision-Making
Avalanche forecasting is a dynamic problem. Forecasting avalanches
means dealing with uncertainty in the form of spatial and temporal variability
in the seasonal snowpack, including incremental in snow and weather conditions.
All seven elements are interconnected.
True. Most victims trigger the avalanche themselves. This suggests that the
perception ( i.e. "the snow is stable" ) did not match reality at the time of the
accident.
Forecasting is the prediction of current and future events.
Errors in human perception are at the root of most avalanche accidents.
The link between avalanche forecasting and risk analysis is formed when
decision-making follows the prediction issued by an avalanche forecast. Since
these decisions involve a chance of losses, the process of avalanche forecasting
and the resulting decision-making is the equivalent of a risk analysis.
Avalanche forecasting is not limited to estimates of instability. There is
a connection between avalanche forecasting, decision-making, and the inherent risk
of those decisions.

I. Definition Of Avalanche Forecasting

Avalanche forecasting is the prediction across space and time of
current and future snowpack instability relative to a specific triggering level.
The spatial and temporal variability of the seasonal snow cover is the
principle physical uncertainty in avalanche forecasting.
Avalanche forecasting is defined in terms of instability.
Whereas traditionally, avalanche forecasting was defined in terms of stability.
Information that reveals instability.
Triggering level refers to the amount of energy required to release an avalanche.
Forecasting for natural releases, forecasting for skier triggering, forecasting for explosive triggering.
Most slab avalanches release from overloading by precipitation or wind.
True.
Sometimes slabs release due to temperature change. Temperature change ( usually an increase )
results in slab motion which leads to deformation. If there are pre-existing weaknesses such
as slip surfaces or shear bands, the additional deformation produces the propagating shear
fractures required to release an avalanche.
The energy required to release a slab depends largely on the size of imperfections and
the parameters of the load applied at any given time. In this case, parameters of load applied means
intensity, which is expressed roughly by the amount of force and the rate at
which the force is applied ( the balance between shear stress intensity
and shear fracture toughness in the weak layer ).
At all times, but especially during times of conditional instability ( the
prevailing state ), the size, state, quantity, and distribution of weaknesses and
imperfections ( such as weak zones and weak interfaces ), and the energy required to
trigger a slab release on any such weakness, are unknown. Therefore avalanche forecasting
can be reduced to encounter probability and trigger probability, i.e.
"what is the chance of encountering a critical imperfection and how much energy
will it take to trigger an avalanche". These probabilities give avalanche forecasting
its risk-based character.

II. Goal Of Avalanche Forecasting

The goal of avalanche forecasting is the reduction of uncertainty introduced
by three key sources:
- Temporal and spatial variability of the snow cover, including terrain influences.
- Incremental changes to the snowpack from snow and weather conditions.
- Human factors, especially variations in perception.
From the human perspective, avalanche forecasting seeks to align perception
and reality, i.e. human perception of instability across the spatial and temporal
scales should match reality as closely as possible.
Aligning human perception with reality is accomplished by performing objective
analysis on data relevant to the case at hand ( using the scientific method ).
In the context of avalanche forecasting, relevant information is any information
that reveals instability.
False.
False.
Redundant information degrades the accuracy of predictions.
Data classifications are as follows:
- Class I. Instability Factors. Non-numerical, mostly observable phenomena.
  Includes avalanche occurrences, shear quality, instability tests, cracking of the
  snow cover, and whumpfing.
- Class II. Snowpack Factors. Rule-based. Snow stratigraphy, snow temperature,
  grain size and type, snow density.
- Class III. Snow and Weather ( meteorological ) Factors. Precipitation, wind,
  temperature, radiation, weather forecast.
An ensemble forecast is the average of several predictions. It is thought that
ensemble averages are more accurate. These forecasts are often used as a hedge against
chaos. Ensemble forecasts have improved weather forecasting.

III. Human Factors And Perception

Failures in human perception with respect to avalanches run from the
level of individual to the level of government and
society. It is possible for a single individual to experience a
serious perception failure and trigger an avalanche while skiing. On the
other end of the scale, it is possible for an entire society to experience
a serious perception failure and fail to allocate sufficient resources to
avalanche forecasting, hazard mapping, and zoning.
Perception is a view of reality based on information processing by
the senses.
Human influences on perception are roughly divided into the following categories:
- Basic personality traits and behaviour ( risk propensity ).
- Individual perception and its effect on decision-making.
The relationship between risk propensity and decision-making is highly
complex, but in general risk-taking propensity is governed by the total
sum of one's life experiences.
The Risk-Decision matrix displays the relationship between
risk propensity, perception, and decision-making.
The operational risk band is a framework defined
by the upper and lower limits of risk. To avoid errors that
result in either accidents or excessive conservatism, the results
of all decisions should fall inside the operational risk band. This
is an important component of formalized decision-making.
The upper limit of the ORB is a Type I error, usually resulting in an accident.
The lower limit of the ORB is a Type II error, usually resulting in lost opportunity.
Reluctance to claim the snowpack is unstable unless hard proof is at hand.
Failure to open an important transportation corridor.
Target risk is the maximum risk an individual is willing to accept for
a given reward. Target risk optimizes the difference between potential gains
and potential losses. Behaviour modification is the typical method
by which people seek to achieve target risk. For example, people might
be willing to take a serious risk for a serious reward but usually are
unwilling to take a serious risk for a small reward. Achieving target risk
means that options are weighed based on the difference between risk and the reward
across the series of options, with the option having the largest difference chosen
most frequently. ( Relative to the individual and their risk propensity,
which is of course, a complex subject by itself ). In the bigger picture,
it is extremely important to understand how one's perception of risk and reward,
influence decision-making. The ORB is a framework used
to formalize decision-making with customizable upper and lower limits on risk.
The upper and lower limits are set by an organization. ( Or an individual although
most individuals probably do not consciously consider the ORB in their decision making process. )
Death, accidents, injuries.
Serious financial losses, lost opportunities, bruised egos.
Variations in perception increase with uncertainty.
Gerald Wilde
When safety devices are used, people modify their behaviour to
maintain the same level of risk as before. When avalanche beacons
are used, people choose to ski riskier terrain than they would ski
without an avalanche beacon. Therefore the overall level of risk
remains the same. The long and the short of this effect is that
using a safety device will affect your decision-making and this awareness
is a critical element of objective decision-making.
Targeted education and experience improve perception.
Biases degrade perception.
Biases have a small effect on perception of instability
when instability is widespread and the triggering energy is low.
Biases have a large effect on perception of instability when
instability is not quite isolated and the triggering level is a
bit higher than usual.
During times of absolute instability, most people, especially
experienced people, agree that the snowpack is unstable. Therefore
variations in perception are small.
During times of conditional instability ( the prevailing state ),
people may or may not agree about the quantity or location of instability, nor
about the required triggering energy. Therefore variations in perception
are large.
Perception of instability relative to the public danger scale clearly
shows that many fatalities are linked to the Considerable danger level, which
proves that perception during conditional instability is poorest ( or
has the largest variations, depending on your perspective ).
Diagram omitted.
Data sampling is one of the most crucial inputs into any forecast. In fact,
it is fair to say that data sampling forms the basis of forecasting,
especially for backcountry travel. Therefore, if the data sampling is subject
to bias, the forecast is not objective. For example, if a slopeside test
reveals nothing about instability, it can be easy to conclude that instability
is not present. However the choice of test location plays a critical role in
the test results. This is a perfect example of how biased data sampling
could lead to a disaster.
White argues that perception of hazard does not improve with the level of general education, i.e., high school graduates vs. college graduates.
Most accidents occur during Moderate or Considerable danger.
Storm snow instabilities are found near the surface; this type of
instability is much easier to find or detect through skiing. Storm
snow instabilities are also subject to far less perceptual error than
deep instabilities because biases strongly affect deep instabilities,
especially when instability persists for a long time. ( i.e. Recency or Frequency. )
No
The temporal and spatial variability of the snowpack, in addition
to the danger of accessing real avalanche starting zones, often mean
that the results of slopeside tests are, for all intents and purposes,
random or chaotic ( like the lottery ). In addition, data sampling is
subject to bias ( leading to serious perceptual errors ) that can add an element of
Russian Roulette. In this case, not only might you "not win" any money,
you also might suffer serious injury or loss of life.

IV. Reasoning Process

The two main types of reasoning used in avalanche forecasting are as follows:
- Inductive. Inductive reasoning is intuitive and integrative; much more
  difficult to characterize than deductive reasoning. ( The inductive
  reasoning process differs from person-to-person. ) Inductive reasoning
  relies on a conclusion to establish a truth.
- Deductive. Deductive reasoning relies on models, procedures, and
  data to arrive at a result. Deductive reasoning relies on a truth to
  reach a conclusion.
An example of each type of reasoning is as follows:
- Inductive. Looking a steep slope that has shed its snow
  after a storm and understanding why the slope is safe to ski.
- Deductive. Examining weather station data.
Snow stability is dynamic and evolutionary, therefore avalanche forecasting is dynamic and evolutionary.
Rapid changes to the snowpack, across both space and time, underpin the dynamic nature of avalanche forecasting.
The dynamic process of integrating information about instability using inductive reasoning is somewhat analogous to Bayesian revision using updated information as time proceeds.
With the first snowfall of the season. However, an avalanche atlas that contains
historical information about the path is also very useful in assembling probabilities
used in forecasting.
New information can make previous information worthless; since avalanche
forecasting is dynamic and evolutionary, the process of forecast revision is
on-going. However all new information, including information that reveals
instability, must be integrated into the complete seasonal forecast, including
any historic data available.
The definition of Bayes Theorem is as follows:
- Posterior a Likelihood × Prior and proportional to
The previous forecast constitutes the prior if avalanche forecasting is viewed
as a Bayesian process.
Singular information relevant to the current situation constitutes the likelihood
if avalanche forecasting is viewed as a Bayesian process.
The new forecast constitutes the posterior if avalanche forecasting is viewed as
a Bayesian process.
One datum can completely change the opinion of the outcome if the datum
reveals information about instability. This is particularly true if a low-entropy
( low uncertainty ) datum reveals instability. For example, forecasting is conducted
before a ski trip and moment-by-moment during the trip. Even if the current forecast
is "isolated instability", the appearance of cracks beneath the skis changes the
entire forecast immediately. In this case the current forecast is revised from "isolated
instability" to "high instability" regardless of the prior forecast and the posterior
( the prediction ) is revised to "avalanche" from "no avalanche".
An avalanche atlas constitutes distributional information ( the prior ) in the
context of avalanche forecasting.
False.
Instability is highly time-dependent; for example, solar warming
can increase instability for a few hours during the afternoon. Instability may
fall almost immediately when the slope falls into shade.
Information from models, rules-based systems, and telemetry data.
The information database for helicopter skiing is very deep and detailed.
Information on prior seasons is available as well. For ordinary backcountry skiing,
the information database is much smaller and relatively little historical information
is available.

V. Information Types And Relation To Perception

Avalanche forecasting relies on the following types of information:
- Singular Information. Information relevant to the current situation and near future.
- Distributional Information. Information from the past or from similar situations in the past.
Yes
Go find the information.
Go test ski a few slopes, dig a few snow pits, read current telemetry and weather forecasts.
Yes
Informational entropy refers to the level of uncertainty associated with
any data. Relative to avalanche forecasting, both cracking in the snow cover
and natural avalanche releases provide extremely reliable, i.e. low uncertainty,
information about instability. On the other hand, a report of wind speed and
direction is indirectly linked to instability. Understanding and linking concepts
is required to convert high entropy data into low entropy data.
Cracking of snow cover is an obvious sign of instability; cracks mean
that propagating shear fractures are occurring. Wind speed and direction
is linked indirectly to instability.
Highly correlated means there is an indirect relationship between
two elements in a system. This loosely coupled relationship means that
a change to one element in the system may or may not result in a change
to the other element in the system and/or the change may be difficult to
predict or ascertain.
Generally speaking, resolving highly correlated
data requires a thorough conceptual understanding of the systems and data
involved in order to create a link between the systems, or to refine the data
into a format relevant to the case at hand ( e.g., a report of wind speed
and direction must be linked with a visual observation of wind-loaded snow ).
This linkage can only formed if the observer understands the concepts of,
and relationships between, distributional data ( wind speed and direction )
and singular data ( the case at hand, i.e. the visual observation of wind-loaded
snow ). Even if wind-loaded snow is observed, it may be far away and still
irrelevant to the case at hand.
Yes. Priority is given to Class I observations because this type of
data reveals positive information ( highly prized ) about instability. Class II
data only reveals the potential for instability and Class III data only
reveals elements which might ( or might not ) contribute to instability.
In general, any datum which reveals instability is considered more important
than any datum that contains little or no information about instability, regardless
of its class.

VI. Scales In Space And Time

Avalanche forecasting operates at three primary spatial scales that
refer to the geographic area of the forecast: synoptic scale, meso scale,
and micro scale.
Avalanche forecasting operates along the temporal scale, including
the distant past, recent past, the present, and the near future. Avalanche
forecasting typically does not operate past the near future because of the
chaotic nature of the data require ( i.e. the accuracy of long range
weather forecasts is far from assured ).
Scale matching involves resolving the scale of information to the
scale of the forecast. For example, one should not rely solely on a synoptic
scale forecast for decision-making at the micro scale. The synoptic forecast
is important but cannot take precedence over information relevant to the
current situation. If one observes natural avalanches or cracking in the
snow cover, one can assume high instability regardless of the information
contained in the synoptic scale forecast. Fundamentally, scale matching is necessary
because information found at one scale cannot be simply applied to
another scale. Seeing cracks in the snow cover at one location in the mountains does not
mean the snow is unstable for 100 miles in every direction.
Quantity, rate, and duration of snowfall is another good example. Most
quantitative precipitation forecasts are issued at the synoptic or meso
scale. At the micro scale ( very local ) one may find far less or far
more snow than indicated by a synoptic scale forecast.
Despite local signs of instability, a backcountry traveler might rely on
a synoptic scale forecast and decide to ski an unstable slope. This could
result in an avalanche. This is a good example of the link between the
dynamic, evolutionary nature of avalanche forecasting and the use of
singular and distributional information. The synoptic scale forecast
constitutes distributional information; local signs of instability constitute
singular information relevant to the case at hand.
The three primary spatial scales are as follows:
- Synoptic. This is the largest scale: 1000 square kilometers.
- Meso. This is the middle scale: 100 square kilometers.
- Micro. This is the smallest scale: 1 square kilometer.
True.
As the scale decreases, difficulty of forecasting increases and the need
for accurate information relevant to the case at hand increases as well.
Yes.
A now-cast is a forecast of instability for the present moment.
It is more difficult to forecast instability for next Thursday than for next Wednesday.
Weather is strongly linked to avalanche formation. The ability to
successfully forecast avalanches is strongly influence by the essentially
chaotic nature of weather.

VI. Decision-Making

The following is a basic list of steps used to issue an avalanche forecast:
1. Data collection and integration.
2. Analysis.
3. Objective decision-making.
Formalizing the decision-making process prevents ( or reduces ) bias.
The spatial and temporal variability of the snowpack, in conjunction with
incremental changes due to snow and weather and variations in human perception,
creates the fundamental residual risk associated with avalanche forecasting.

Conclusions

Complex links between the elements of applied avalanche forecast
make it difficult to conceive avalanche forecasting as a chain of events.
Terrain and climate are viewed as distributional information. In general,
terrain and climate are included, implicitly, in most aspects of avalanche
forecasting.

Biases

The search for supportive evidence is expressed as a willingness
to gather facts that support the desired conclusion while disregarding
facts that support an alternate, or undesired, conclusion. To prevent
this bias, always search for information that reveals instability.
Inconsistency is expressed by applying different sets of
decision-making criteria to similar situations. One might use the
presence of existing ski tracks to justify the decision to descend
a steep slope. In this case, the decision is based solely upon the
existence of ski tracks, when without the presence of ski tracks
one might use an entirely different set of criteria to evaluate
instability.
Conservatism is expressed by failure to change one's mind when
new information or evidence becomes available. This can affect
evaluation of instability in either direction, and of course,
this is linked directly to decision-making. Keep an open mind
and use a formalized decision-making process to neutralize this bias.
Recency is expressed by allowing events from the most recent
past to dominate decision-making at the expense of events in the
less-recent past. Consider the current situation ( singular )
and past situations ( distributional ) when making-decisions.
This bias is very important when instability persists for a long
time.
Frequency is expressed by allowing very frequent events to
dominate decision making at the expense of less-frequent events.
Consider the current situation ( singular )
and past situations ( distributional ) when making-decisions.
Availability is expressed when decision-making is dominated
by specific events easily recalled from memory at the expense of
information relevant to the case at hand.
Illusory correlations is expressed a link is "seen" between
data when no such link exists. Deductive reasoning is strongly
affected by this bias.
Selective perception is expressed by viewing a problem in the
context of one's own background and experience. Allow everyone
to have input, especially people with different backgrounds.
Expert halo is expressed by allowing one person's expertise
( real or perceived ) to dominate decision-making. Everyone in
the group ( skiers, forecasters ) should contribute to the decision.
Underestimating uncertainty ( denial ) is a method of coping
with anxiety, especially when the outcome is time-pressured or
may have a serious outcome. Consider distributional and singular
information inside a formalized decision-making process to neutralize
this bias.
Excessive optimism is expressed by denial. Seek the opinion of
a disinterested third party to neutralize this bias.
Anchoring is expressed when initial information is given
more weight in the forecasting process than new information. During
a ski tour, signs of instability might not be present. However if
signs of instability appear, it is possible to try and extrapolate
to the best case scenario, i.e., instability is isolated in this
location only. While this might be true, it is important to remember
that "might" is the operational word.
A rule of thumb is expressed by a rule that greatly oversimplifies
the problem. Consistency ( staticity ) in situation is required for a rule of thumb
to work properly and avalanche forecasting considers a variety of
very specific, and dynamic, situations. Using a rule of thumb
almost guarantees that one will overlook important information
and this will have a negative effect on the decision-making
process.
Clients sometimes pressure guides to travel over terrain that
is too dangerous. An inexperienced client should not be allowed
to override the instability assessment of an experienced guide.
Social proof is expressed by seeing other people doing something
without consequences and believing that one can do the same thing
without consequences. Formalize the decision-making process.

Q & A

2010-12-15T18:29:00.000-08:00

I have been hyperbusy with personal stuff, so thanks for your patience. Today, I'm going to answer a few questions that have been sent my way over the past few weeks.

( Promise a full post tomorrow or the next day-I've managed to read through most of the ISSW 2010 papers, and I've got a few additional remarks that I'd like to make about some recent conversations in which I have participated. )

Do avalanches originate in tree-covered areas?

Good question. Trees definitely alter the snowpack by anchoring snow, intercepting snowfall, intercepting radiation, and by depositing "bombs" and moisture that break up the snowpack.

According to The Avalanche Handbook, avalanches in tree covered areas are infrequent, but they do happen. If you travel in mountainous terrain during the winter, you can rely on very thick tree cover for safety only when there is no avalanche terrain anywhere above the trees.
Avalanches frequently initiate above tree-covered areas and flowing snow travels easily through the trees, even if the trees are thick. Have you ever noticed snow plastered on the uphill side of a tree? This is a good indicator of avalanche activity, and can also be used to determine the height of flowing snow. Remember that forest clearings may be especially dangerous because of instantaneous changes in snow conditions. This means that you can go from safe to unsafe in just a few steps.
Gladed areas are, for all intents and purposes, the same as open slopes. The consequences of taking a ride through the trees are severe. How severe? Think about what might happen if you have a high-velocity encounter with a tree. You can express such an encounter with the following formula: NOTFUN.
You may not be safer in forested areas, and if conditions are very poor, you might actually be less safe. As always, you must use the current terrain, weather, and snowpack to determine the likelihood of avalanche formation, and you must choose terrain appropriate for conditions.
According to researchers, people in North America are much more likely to suffer traumatic injuries during avalanches than their counterparts in Europe. Trees are definitely a contributory factor.
Don't forget about tree wells.

Other facts about trees and the snowpack.

Thick trees anchor the snowpack, which can prevent avalanche formation. On the other hand, trees often serve as trigger points or fracture points. It's a good idea to keep this in mind.
Trees intercept incoming shortwave radiation, which explains why you can find decent snow in the trees several days after a storm.
Trees intercept outgoing longwave radiation and reflect it back into the snow cover, which prevents heat loss. This is why surface hoar doesn't form readily beneath trees, and it's also why you're less likely to find near surface facets underneath the trees unless the temperatures are really really cold.
Trees drop bombs and liquid water onto the snowpack. Large snow bombs break up slabs, and liquid water turns the snowpack into solid concrete when it freezes.

How are buried facets formed?

This is a bit more complicated.

Facets can form inside the snowpack when the air is much colder than the ground on which the snow sits. The strong temperature difference means that water vapour moves quickly toward the snow surface, and a constant replenishment of water vapour means that crystals can grow rapidly. Rapid growth produces angular crystals.
Facets can form inside the snowpack itself when a crust creates a vapour barrier that traps moisture. Over time, with vapour supply and the right temperature gradient, fast crystal growth occurs. Once again, rapid growth produces angular crystals.
Facets can also form at the snow surface. This happens with very cold ambient air temperatures, or when the snow surface becomes intensely cool from longwave radiation loss.
Radiation recrystallisation can also produce facets. This happens when sunlight strikes very cold snow, and usually happens on south faces at at very high elevations.
Finally, facets can form when cold, dry snow falls on wet snow. The wet snow contains heat that sets up a strong temperature difference when it comes into contact with cold, dry snow. Again, as with above, the strong temperature gradient moves moisture rapidly, and constant replenishment of water vapour means that crystals can grow rapidly.

The Life of a Snowflake

2010-12-01T04:45:00.000-08:00

Time is a wheel in constant motion always, moving us along—Lee Ann Womack

Double Post Wednesday. I'm going to be busy for the next few weeks, so I'm posting twice today. The first post, below, is a brief essay on the importance of understanding snow metamorphism- from crystal formation in the atmosphere, through deposition on the ground, and inside the snowpack itself. The second post is a snow metamorphism exam based on Chapter 3 of The Avalanche Handbook. It's ridiculous, but some people will enjoy it.

***

NOTE: This is the third post that will address the general question of Why Is It So Complicated? This time we're going to talk about snow metamorphism. I don't really know how to teach anyone about snow metamorphism, but hopefully this post will provide a basic understanding of why snow metamorphism is important and how it can be applied in the field. In my own experience, I literally cannot imagine making safe decisions without having significant knowledge of snow metamorphism, but this statement applies to me and me alone. As Ed LaChapelle said, there are many ways to forecast avalanches.

If you read this blog often, you may notice that I try to describe things in very literal terms. On first read, this post is going to seem like a departure, because I do use some highly subjective language. Please keep in mind that I do not approach backcountry avalanche forecasting from a mystical perspective; I actively observe the environment—right down to the way the air feels on my nose after a few rapid breaths*—and I draw my observations from the science, not the psychic.

( *A very chilled nose after three rapid breaths means extra caution delivers good skiing. )

Polymorphism

The term polymorphism is the ancient Greek word for many forms and it very neatly describes the heart of the complexity and uncertainty that many people experience when they think about snow crystals. But you and I, we aren't so different from snowflakes, because over our lives, we also react to the dynamic conditions around us, and we too change as a result. Sometimes these changes are for the better, and sometimes they're for the worse.

Ask yourself the following question: Am I the same person I was 5 years ago?

Of course not.

So the simple fact of the matter is that, as with people, snowflakes change with the passage of time. The principles of snow metamorphism are incredibly useful, and in this post I refer to snow metamorphism in the holistic sense: changes to snow crystals in the clouds, changes to snow crystals on the ground, and changes to snow crystals in the snowpack.

The Life of A Snowflake
Snowflakes are born in clouds of supercooled water vapour. Both the temperature and the amount of moisture available for crystal formation vary over time and space in the atmosphere, which means that the neither the temperature, nor the amount of moisture, are consistent. This is responsible for variations in crystal form as the snow falls, and variations in crystal form are very important if you're a backcountry skier.

But let's get back to our snow storm. As we all know, eventually gravity pulls the snowflakes to Earth, where they form a layer. On the ground, the amount of water vapour and the temperature are different than in the clouds, so the snowflakes begin to change. The first observable changes are the loss of branches as the fine details of the snow flake melt. Soon thereafter, as the crystal size decreases, the weight of the snowpack produces overburden pressure that pushes the snowflakes into each other, effectively crushing them and further reducing the pore space. These changes happen in a relatively short amount of time, from a few hours to a few days.

Over the longer term, the temperature gradient determines how quickly water vapour moves through the snowpack, which determines whether or not the snowpack becomes stronger or weaker. Thick, deep snowpacks are strong because moisture transport is slower and weaknesses are crushed and rounded out of existence. Thin snowpacks are weak because moisture transport is fast, which leads to rapid crystal growth and angular shapes with cavernous pore spaces and fewer bonds. Furthermore, cold temperatures preserve existing weaknesses such as crusts and buried surface hoar.

What I Think About
Okay, I've rattled on and on about the delights of snow metamorphism, but what are the practical concerns? Well, having a strong working knowledge of snow metamorphism leads me straight to the following questions:

Are there instabilities in the new snow itself? ( Timeframe: 24-72 hours )
Are there instabilities in the bond between the new snow and the old snow? ( Timeframe: Up to 7 days )
Are there older instabilities and how will they react to loading by snow or skiers? ( Timeframe: Entire winter )

At first glance, this list probably seems quite thin, but continue reading if you'd like to see how a strong working knowledge of snow metamorphism allows me to integrate some very useful details into these broad questions. The first concern is, of course, given the questions above, how can you identify snowpack with dangerous characteristics?

Applying The Principles Of Snow Metamorphism In The Field
If you know what to look for, you can observe these conditions in the snowpack. Recently, I was out on a ski tour the morning after a significant storm. In the Cascades, this generally means that it's time to watch your ass, as snow often arrives in large amounts, and with significant wind. Consider the following list of observations from multiple locations. These observations were based on, or related to, a strong working knowledge of snow metamorphism.

Constant presence of decomposing crystals at the snow surface.
Uniform crystal density in the new snow.
Uniform increase in hardness with depth.
Loss of branches on new snow crystals.
The crystals at the bottom of the snow had fewer branches than the crystals at the top.
The pore space at the bottom was smaller than the pore space at the top.
The bond between the old snow and the new snow was bomber.
Zero slab avalanches.
Very little sluffing.
Few drift lines in the alpine.
Good snow coverage on trees regardless of orientation.

Going Behind The Scenes
Instabilities in new snow are often represented by soft slab avalanches that form in the new snow itself, or by avalanches that form when dense wind slab overlies softer snow below. An understanding of snow metamorphism can help you learn what to look for when you need to determine whether either type of avalanche is likely.

In a perfect blanket of new snow, you should observe uniform increases in hardness with depth. This is often referred to as right side up snow. However, it's not the only possibility. In addition to upside down snow, any new layer of snow could contain internal weaknesses. These usually take the form of a band of heavier snow crystals overlying a band of lighter snow crystals inside the layer of new snow. Suffice it to say, although the new snow might be mostly right side up, it needs to be completely right side up.

Weaknesses of this type form because the atmosphere in which snow crystals form is inconsistent with respect to temperature and the amount of water vapour. This means that the mass and shape of snow crystals can vary. A storm may at first lay down a few centimetres of of light crystals, followed by a few centimetres of heavy crystals, followed by a few more centimetres of light crystals.This creates a complex layering that is highly suitable for avalanche formation; even though the snowpack is mostly right side up.

Wind slab is upside down snow, but it forms for different reasons. Snow crystals shatter when moved by the wind, and they form a fine dust-like mist that accumulates on lower density snow in sheltered areas. Over the course of a few hours, this fine mist turns into a thick layer of tiny crystals. The tiny grains have a high number of bonds per unit volume, and this enables them to knit together very rapidly. However, the new snow below may not be able to support the weight of the slab, and avalanches form quite easily when you crush the weaker snow below by applying a dynamic load to the wind slab. In an instant you have something on top of nothing, and an instant later you have an avalanche.

For older weaknesses, there are two concerns over the long term: favourable metamorphism that comes with depth and relative heat, and overburden pressure that slowly crushes weaknesses and fills in the pore spaces. Obviously, without a working knowledge of snow metamorphism, it's going to be pretty hard to know what to look for. I'm not comfortable writing much more about older weaknesses, because research also shows that they're not very manageable. Therefore, unless you have professional-grade knowledge, you should avoid trying to diagnose these problems.

This might seem complicated, but it's much easier to understand if you have a decent working knowledge of snow metamorphism across various scales of space and time. On the day of our trip, we had deep, stable snow that was well-bonded to the old snow below. I was very comfortable skiing in steep avalanche terrain without constantly feeling the need to look over my shoulder.

Conclusion
Much of the information used during my recent trip was pulled directly from the principles of snow metamorphism. I sometimes hear people say that introductory avalanche education should focus less on snow metamorphism and more on decision-making. This makes me scratch my head in confusion.

How can you make critical decisions about snow when you know almost nothing about it? Continuous avoidance of avalanche terrain simply isn't compatible with realistic human behaviour, and you can't travel safely in avalanche terrain if you don't understand snow.

Perhaps this winter I will turn my brain toward developing a realistic, usable framework for understanding snow metamorphism. Of course, it might not be possible to develop this framework, in which case, I'll point you straight at This Little Monster.

Snow Metamorphism Exam

2010-12-01T02:46:00.000-08:00

255 questions from chapter 3 of The Avalanche Handbook. Questions start with green headings and answers start with red headings. I'm not sure how long it will take to complete this exam, but I can guarantee that you will gain professional-level knowledge about snow metamorphism if you master 90% of this material.

Yes, I am fully aware that this exam is ridiculous, but it was a lot of work, so have fun.

Capsule

This chapter discusses snow formation from cloud to ground, including in-depth information on snow metamorphism and its links to avalanche formation.

Snow Crystal Formation And Growth in The Atmosphere

Variations in snow crystal type are responsible for some avalanches. True or False?
Explain this relative to potential instability in new snow and old snow.
Clouds are composed of what elements?
Inside an air mass, what specific process leads to cloud formation?
List two types of particles that serve as condensation nuclei?
What is the typical diameter of such a particle?
Condensation nuclei are rare. That's why you don't see clouds everywhere. True or False?
When does formation of ice crystals become possible?
Ice crystals always form when the temperature reaches 0 degrees Celsius. True or False?
What is the typical size of a water droplet in a cloud?
What is the typical concentration of water droplets in a cloud?
What two elements are required for ice crystal formation above -40 degrees Celsius?
Freezing always takes place at constant temperatures in clouds. True or False? Explain.
At what temperature will water droplets freeze by themselves?
What two processes determine subsequent growth once an ice crystal has formed?
Describe the initial process of crystal growth.
Describe the secondary process of crystal growth.
Branches form from which mechanism?
Branches are destroyed by which mechanism?
What process creates graupel?
What process forms hail?
Describe a novel use for graupel ( Be creative. Invent something. ).
What is the most important variable with respect to crystal form?
What are the two primary crystallographic axes?
How many intrinsic axes are found along the base axis?
Describe the symmetry of the basal plane.
Along which axis does heat flow most efficiently?
Platelike crystals form from growth along which axis?
Needlelike crystals form from growth along which axis?
Why are crystals six-sided?
Is rate of growth a strong factor in final crystal shape?
At low excess vapor density, what shape is produced regardless of temperature?
What vapor quantity condition is implied by a complex crystal?
Describe vapor and temperature regimes.
Crystals that fall through a cold atmosphere are larger. True or False?
Name one crystal type that often serves as a future sliding layer?
Changes between crystal type or riming can result in poor bonding between layers. True or False?
________ ________ are expected at low vapor density; ________ ________ are expected at higher vapor density.
Explain the concept outlined by the previous sentence.
Define the terms behind the acronym "ACMG"

Classification Of Newly Fallen Snow Crystals

How many levels of classification are typically used to describe new snow?
Describe each level.
How many crystal classifications are used in each?
Describe the typical crystal composition of new snow in simple terms ( not by specific crystal type ).
What effect does this have on avalanche forecasting?
What crystal type is of particular importance? Why?
Describe the correct process for crystal identification at the snow surface.
How do you measure and record the size of snow crystals in the field?
List the levels used for crystal grain size classification, including name and size.

Surface Hoar: Formation And Growth Conditions

Provide the common definition for surface hoar.
Under what condition does surface hoar form? Be very specific.
What is the result of this condition? Be very specific.
Provides a visual description of surface hoar.
What are the two conditions for continued growth of surface hoar?
Surface hoar usually forms on ________ ________ ________ with ________ or ________ ________ conditions in the ________ ________ of ________.
Slight air movement destroys surface hoar. True or False?
Describe the rate of air motion necessary for vapor replenishment.
How would an observer regard these conditions?
What happens if air motion is turbulent?
What usually creates the temperature gradient necessary for surface hoar formation?
________ % humidity is usually required for rapid growth.
Below the % of humidity specified above, surface hoar growth is not possible. True or False?
Describe one scenario during which formation of surface hoar might be expected.
Clouds, especially high, thin clouds, enhance surface hoar formation by contributing moisture. True or False?
If true, explain. If false, explain.
If clouds are present, what factor determines their effect on surface hoar formation?
Describe a terrain feature that might inhibit surface hoar formation.
Why does this terrain feature inhibit surface hoar formation? Be very specific.
Surface hoar forms readily under forest because forest has a sheltering effect. True or False?
If true, explain. If false, explain.
Mountain guides often call logged clear cuts "lunch counters". True or False?
If true, explain. If false, explain.
Avalanches are rare in clear cuts. True of False?
If true, explain. If false, explain.
In what snow climate is surface hoar found? Be very specific.
Once formed, surface hoar is extremely strong. This is why it persists for such long periods. True or False?
Describe three conditions that might destroy surface hoar.
Surface hoar is sometimes a more significant problem at lower elevations. True or False?
If true, explain. If false, explain.
In addition to being pretty, surface hoar is good at producing ________ ________ ________.
What is the term used to describe the mechanical strength of surface hoar?
What does this term mean?
Why is this important?
What provides energy to drive a fracture forward when surface hoar is disturbed?
It is only safe to travel across buried surface hoar on flat terrain. True or False?
If true, explain. If false, explain.
How might surface hoar gain strength?
What layer variable determines how long surface hoar remains unstable?
What is the range of size for surface hoar crystals?
Surface hoar is often described as a ________ ________. Or ________ ________ ________ ________.
Unlike facets, surface hoar is easily destroyed, and therefore not responsible for major avalanches. True or False?
Wild-harvested, Selkirk surface hoar is highly prized as both a recipe ingredient and ice cream garnish at fancy restaurants in Japan. True or False?

Snowpack Temperatures And Temperature Gradients

What serves as the upper and lower boundaries for winter snowpack?
What is the temperature of the lower boundary and why?
What is the temperature of the upper boundary and why?
Which boundary is usually cooler?
Define diurnal fluctuation.
Define the two elements of a temperature gradient in terms of a bipartite vector.
How is the temperature gradient expressed?
What is the term for a snowpack that lacks a temperature gradient?
What can you assume about this snowpack?
When does this occur?
Describe, in very simple terms, the quality of the temperature gradient in a maritime climate.
Why is this the case?
Describe, in very simple terms, the quality of the temperature gradient in a continental climate.
Why is this the case?
What explains the very general difference in character of avalanching in these climates?
As shown above, crystals are dependent on climate, not physical processes. True or False?
Certain crystal types are not found in some snow climates. True or False?

Snowpack Temperatures And Temperature Gradients

Once deposited on the ground, how many minutes must pass before snow crystals begin to change form?
Why do these initial changes cause direct-action, loose-snow avalanches?
Why do crystals change form?
What is the range of typical values for supersaturation in the atmosphere?
What is the range of typical values for supersaturation in the snowpack?
New snow crystals are highly stable. True or False?
What ratio and quantity describes unstable crystals?
In very general terms without regard to specific crystal type, which crystals are most stable?
In very general terms without regard to specific crystal type, which crystals are least stable?
What shape has the minimum surface area to volume?
What effect might crystals of this shape have on stability of crystal shape?
What causes the disappearance of intricate crystal branches?
Vapor pressure over a ________ surface is higher than vapor pressure over a ________ surface.
Therefore, what crystal shape quality promotes sublimation?
Where does this water vapor go?
What is the implication of the production of water vapor via sublimation?
Saturation vapor pressure increases by what percent across what temperature range?
What is the implication of this?
List the three factors that influence metamorphism in dry snow.
Define each factor.
Where is the temperature gradient usually highest?
This region is defined as the ________ ________ ________ ________ ________.
What are the two key factors that determine rate of metamorphism for dry snow?
What is the initial result of branch disappearance with respect to crystal size?
What is the name for this process. Be very specific.
What happens next? Why?
________ particles grow at the expense of ________ particles.
Average particle size ________ when a mixture of sizes is present.

Dry Snow Metamorphism In The Seasonal Snow Cover

Why are the variety of crystal forms limited inside the snowpack?
The term metamorphism includes changes to form induced by these two factors.
What snowpack-related force rearranges grains in the snowpack?
Relative to crystal configuration in the snowpack, what is the result of this rearrangement process?
How might this affect both stability and instability in the short and long term?
What process dominates shape change in glaciers or firn snow?
What is the primary difference between crystal formation in the atmosphere -vs- in the snowpack?
How does the temperature gradient influence vapor diffusion? Be very specific.
What is the general result with respect to motion of water vapor?
Specifically, how does mass transport occur under this effect?
What determines crystal forms that develop under this recrystallization process?
With respect to water vapor, rate of motion increases as these three factors increase.

Crystal Forms In Dry, Seasonal Alpine Snow

Growth rate and crystal form are more dependent on pore size than temperature gradient. True or False?
If true, explain. If false, explain.
High temperatures, large temperature gradients, and large pore spaces result in what growth rate?
Low temperatures, small temperature gradients, and tiny pore spaces result in what growth rate?
What is the critical temperature gradient required to produce faceted crystals?
How do you measure a temperature gradient?
Faceted forms and highly angular snowflakes develop because of similarities between vapor saturation conditions in the atmosphere and snowpack. True or False?
Why does depth hoar only form near the ground? Be very specific.
Why do facets form slowly in very cold snow? Be very specific.
At high growth rates, what crystal forms are expected?
At low growth rates, what crystal forms are expected?
What affect might growth rate have on snowpack instability?
List three examples of crystals types produced at high growth rates.
High growth rate crystals form preferentially in what type of snow climate?
Connect the number of avalanche fatalities in Colorado with its snow climate.
Which are the top five states with respect to avalanche fatalities?
Large pore spaces present favorable conditions for what type of crystal?
What pore space quality inhibits development of facets?
Describe a method used to decrease pore space in depth hoar and when this method must be implemented.
Depth hoar is always weak. True or False?
What is near-surface faceted snow?
What are the persistent forms? Explain each type.
What are mixed forms?
Crystals developing under the slowest growth rates are referred to as ________.
Crystals developing under the highest growth rates are referred to as ________.
Draw the symbol for "new snow or precipitation particles".
Draw the symbol for "decomposing and fragmented precipitation particles".
Draw the symbol for "rounded grains ( monocrystals )".
Draw the symbol for "faceted crystals".
Draw the symbol for "cup-shaped crystals; depth hoar".
Draw the symbol for "wet grains".
Draw the symbol for "feathery crystals".
Draw the symbol for "ice masses".
Draw the symbol for "surface deposits and crusts".
Why was the term "equitemperature metamorphism" discarded?
Why was the term "temperature gradient metamorphism" discarded?
What is the name for the crystal type that constitutes the largest size found in the snowpack?
Why are these crystals the largest?

Growth Of Crystals Around Crusts In Dry Snow

How does a crust influence crystal formation?
With respect to crusts, what is the most important feature for avalanche formation?
Why do facets sometimes grow directly beneath a crust?
What leads to dry/wet faceting?

Bond Formation In Dry Alpine Snow

Formation of bonds is also referred to as ________.
How does bond formation occur?
Where do bonds form?
What is found at the boundary between two crystals?
Describe the perspective from which experimental work on bond formation in dry snow has been conducted.
What is the final angle of the dihedral?
Stress along the grain boundary is constant. True or False?
If true, explain. If false, explain.
Describe the process of bond formation relative to rate of bond formation over time.
Discuss how differences in crystal size affect stability with respect to bond formation.
Thermodynamic processes occur ________ at ________ temperatures.
What is the temperature threshold for persistence of instability in new snow?
In theory, what exists at the surface of crystals? What happens to this theoretical region as temperature increases?
When the temperature gradient is high, mass transport is ________.
Discuss the spatial characteristics of vapor deposition under a high temperature gradient.
If avalanches released easily on depth hoar, what conclusion could be drawn about travel in continental climates?
What conclusion is reached instead?
When snow falls at high temperatures, rapid bond formation decreases what?
Discuss bonds / unit volume with respect to grain size.
What is necessary for bond formation between adjacent layers of snow?
How does the degree of riming effect bond formation?
Broken crystals are usually small. What effect does this have on bond formation?
List the integrated elements of bond formation and layer strength for dry snow.
Fractures originate at what scale relative to the size of an individual bond?
Why is this important?
What is the most important temperature effect on dry slab-formation relative to avalanche forecasting?
Discuss the nature of bonding and strength increases for the persistent forms.
Mismatches in crystal type enhance bond formation because opposites attract. True or False?
Where do persistent forms originate? Name the exception.
What do studies of avalanche fracture lines suggest about layering and bonding?
What information about layering and bonding can one derive from instability tests?

Persistent And Non-Persistent Weak-Layer Forms

Who coined the term "persistent forms"?
What are the characteristics of the persistent forms?
What are the characteristics of the non-persistent forms?
Discuss human perception with respect to persistent forms.
Discuss human perception with respect to non-persistent forms.
When do non-persistent forms originate?

Metamorphism Of Wet Snow

What happens to heat flow and metamorphism in wet snow?
Wet snow can consist of what three materials?
Discuss the relationship between melting point and particle size.

Snow With High Water Content

Discuss particle separation in wet snow. Include the percentage of water content by bulk volume required for complete grain separation.
What drives metamorphism in water-saturated snow?
In theory, when does metamorphism stop?
Since differences in melting temperature due to curvature is very small in wet snow, why does metamorphism occur rapidly?
Define "dry snow".
Define "moist snow".
Define "wet snow".
Define "very wet" snow.
Define "slush".
What is a pendular regime?
What is a funicular regime?

Snow With Low Water Content

At what level of water content does grain growth occur through vapor flux?
Relative to the pore space, what develops as water content in wet snow decreases?
What is the result of this?
What is the distinguishing visual feature of moist snow?
What is responsible for this occurence?
How can you differentiate between wet and dry snow?
What is the most accurate method of measuring the water content of snow?
As water content increases, what can you expect about grain growth?

Classification Of Wet Snow

Does the grain classification of faceted snow change when it becomes wet? Explain.

Bond Melting And Formation In Wet Snow

What has the highest heat conductivity of all common substances?
Describe what happens to the melting point of grains when grains touch in water saturated snow.
Describe the process of melt-freeze metamorphism.
What is the colloquial term for snow crystals created by melt-freeze metamorphism?
How do melt-freeze crusts contribute to avalanche formation?

Snow Crystal Formation And Growth in The Atmosphere

True
Variations in crystal size and type can lead to poor between layers of new snow. This causes new snow instability.
Later, these variations can result in grain size mismatch and poor bonding between layers of old snow. This
causes deep instability.
Water droplets
Condensation of water molecules onto condensation nuclei.
Salt, dust, soil, spores.
1 micrometer.
False. Condensation nuclei are always in abundant supply.
At 0 degrees Celsius.
False
20 micrometers.
Several hundred per cubic centimeter.
Freezing nuclei and and temperatures below 0 degrees Celsius.
False. Water droplets can remain in liquid phase ( supercooled ) at temperatures below 0 degrees Celsius.
-40 degrees Celsius.
Vapor pressure gradients and riming
Water molecules are deposited directly on tiny ice crystals by vapor pressure gradients in the cloud.
Riming occurs as the enlarged crystal falls through the atmosphere and collides with water droplets.
Vapor deposition.
Riming
Riming, long growth period, multiple passes through clouds on thermal updrafts.
Multiple passes through freeze-thaw cycles in clouds.
Graupel makes a festive decoration for mountain martinis or other cold beverages.
Temperature
A and C or planar and vertical.
Three. Separated by 120 degrees.
Hexagonal
Along the C ( vertical ) axis.
A
C
Hexagonal symmetry of the A axis.
Yes
Columns
High quantity of water vapor or high supersaturation.
Vapor regime is a specific area with a specific level of saturation. A temperature regime is a specific area at a specific temperature. Clouds often have multiple vapor and temperature regimes.
False
Stellars
True
Rounded forms are expected at low vapor density; edges and corners are expected at higher vapor density.
Slow growth, from low vapor density, produces rounded forms. Fast growth, from high vapor density, produces angular forms.
Attractive Canadian Men on Glaciers.

Classification Of Newly Fallen Snow Crystals

Two
The first level uses the "+" symbol to describe all new precipitation in a single category. The second level uses five crystal types, and three irregular crystal types, to sort precipitation into specific forms.
1, 8
Mixed, or a variety of types are mixed together.
This can complicate decision-making.
Stellars - because they're flat and often form sliding layers.
Use a loupe to determine the predominant crystal type in a sample.
Place crystals on a millimeter grid and provide a range of sizes, i.e. 0.2 to 0.5 millimeters.
Very Fine 0.2mm, Fine 0.2-0.5mm, Medium 0.5-1mm, Coarse 1-2mm, Very Coarse 2-5mm, Extreme >5mm.

Surface Hoar: Formation And Growth Conditions

Frozen dew
When the water vapor pressure of air exceeds the water vapor pressure of ice crystals on the snow surface.
Sublimation of water directly onto the snow surface.
Large, glittering, feathery crystals.
Sufficient water vapor and temperature gradient at the snow surface.
Surface hoar usually forms on clear, cold nights with calm or nearly calm conditions in the lowest meter of air.
False
A few centimeters per second.
As calm or similar to air motion in an enclosed room.
Destroys the temperature gradient.
Long wave radiation loss.
70 % humidity is usually required for rapid growth.
False
If a cold front passes after an overcast day.
False
Clouds can destroy the temperature gradient by preventing loss of long wave radiation.
The temperature difference between the cloud and the snow surface.
Concavity
Long wave radiation is reflected back onto nearby snow ( parabolic / anti-diffusion effects ), destroying the temperature gradient.
False
Forest cover inhibits loss of long wave radiation, which prevents formation of temperature gradient.
False
Mountain guides often call logged clear cuts "surface hoar farms".
False
Surface hoar formation and clear ground suitable for loading result in avalanches that release in clear cuts.
Any climates, provided conditions necessary for formation are met.
False
Wind, sun, rain.
True
Often, surface hoar is easily destroyed by high winds and harsh conditions found at higher elevations.
In addition to being pretty, surface hoar is good at producing propagating shear fractures.
Anisotropic
Weaker in shear than compression.
When surface hoar is loaded, force is transferred from compression to shear.
Collapse
False
Even on flat terrain, movement over buried surface hoar can result in shear fractures that travel uphill to release an avalanche above the traveler.
Bond formation with adjacent layers.
Thickness
1 millimeter to several centimeters.
Surface hoar is often described as a persistent form.Or pain in the ass.
False. Surface hoar is easily destroyed before burial but once buried persists for a long time because its compressive strength means it resists strength by overburden.
True or false are acceptable answers.

Snowpack Temperatures And Temperature Gradients

Lower boundary = ground. Upper boundary = air.
0 degrees because of stored heat from summer ( most important ) and geothermal heat from the Earth's core.
Variable. The air temperature is set by the atmospheric conditions.
Upper
Daytime warming, nighttime cooling.
A vector having both magnitude and direction.
In degrees Celsius per meter.
Isothermal
It contains water.
Spring
Weak
Predominantly warm temperatures and deep snowpack.
Strong
Predominantly cold temperatures and shallow snowpack.
The crystal forms produced are very different.
False
False

Snowpack Temperatures And Temperature Gradients

Zero
Loss of branches causes loss of cohesion through reduction in static friction.
Differences in supersaturation/temperature between the snowpack and the clouds.
Tens of percents
1%
False
Large ratio between surface area and volume, i.e. dendrites -vs- spherical crystals such as graupel.
Round forms.
Angular forms.
Sphere
Spherical crystals retain their original form for a long time.
Vapor pressure over sharply curved branches is very high.
Vapor pressure over a convex surface is higher than vapor pressure over a concave surface.
Sharpness, Angularity, Edges, Creases
Into the surrounding air.
Water vapor is available for additional crystal development.
300% between -15C and 0C.
This is the primary factor in metamorphism, rather than curvature effects.
Temperature gradient, grain curvature, overburden pressure.
Definition of each factor:
- Temperature Gradient. Difference in temperature between snow at depth and surface of snow.
- Grain curvature. The curvature of each grain in terms of convexity or concavity.
- Overburden Pressure. The effect of the weight of snow above rearranges grains and produces contact points for bond formation.
Surface regions of the snowpack.
This region is defined as the top few tens of centimeters.
Temperature of snow and the temperature gradient.
Decrease in crystal size.
Destructive metamorphism.
Destructive metamorphism supplies water vapor, which in the presence of a temperature gradient moves through the snowpack and provides a means for ongoing changes to crystal form.
Larger particles grow at the expense of smaller particles.
Average particle size increases when a mixture of sizes is present.

Dry Snow Metamorphism In The Seasonal Snow Cover

Crystals are insulated by neighbors and physical conditions are slow to change.
Temperature and overburden pressure.
Overburden pressure
Pore space is decreased, crystals touch each other and form bonds.
Affect On Instability- This is is how slabs are formed. In the short term, this may result in enough cohesion for slab formation and release if a weak layer/interface is present. Affect On Stability- This process usually increases the hardness ( and therefore strength ) of the snowpack.
Overburden pressure
The amount of supersaturation in the air surrounding the crystals.
Warmer air holds more water vapor than colder air. Therefore water vapor pressure is higher at the bottom of the snowpack. Water vapor moves up through the snowpack in a hand-to-hand process.
Water vapor moves up through the pore space.
Water molecules move from the top of one crystal to the bottom of the crystal above.
Rate of motion
Temperature gradient, temperature, and pore space.

Crystal Forms In Dry, Seasonal Alpine Snow

False
While all both factors are important, temperature gradient is more important than available pore space ( second order effect ).
High
Low
10 degrees Celsius / meter
Measure temperature at bottom of snowpack and air temperature above. Or measure temperature of layers.
True
Temperatures are high and a lot of water vapor is available for fast crystal growth.
Temperatures are low and water vapor is in short supply. This means slow crystal growth. High supersaturation and high temperatures are required for fast crystal growth.
Facets
Rounds
Faceted crystals are weak. Therefore a high growth rate produces crystals that foster/increase instability.
Surface hoar, depth hoar, facets.
Continental
Much of the Colorado snowpack is composed primarily of weak forms such as facets, depth hoar, and surface hoar because of high temperature gradients created by cold surface temperatures.
Colorado, Alaska, Washington, Utah, Montana ( CAWUM )
Facets
Small pore spaces, tightly packed crystals.
Bootpacking during the early season.
False
Facets produced near the top of the snowpack by temperature gradients, radiation recrystallization, crust influence, or dry/wet snowfall mixes.
The persistent forms are surface hoar, facets, depth hoar, and combinations of these with crusts.
- Surface hoar. Feathery crystals produced by high humidity and long wave radiation cooling that creates a large temperature gradient at the snow surface.
- Facets. Angular crystals produced by high temperature gradients.
- Depth Hoar. Angular, cup-shaped crystals produced at the bottom of the snow by high temperatures and larger quantities of water vapor.
- Crusts. Crusts are a persistent form once buried. You can find combinations of persistent crystal forms with crusts such as facets above/below a crust, or surface hoar above a crust.
Crystals with rounded and angular elements, usually transitions between round-to-facet or facet-to-round. These transition processes are called "faceting" or "rounding".
Crystals developing under the slowest growth rates are referred to as rounds.
Crystals developing under the highest growth rates are referred to as facets.
+
/ ( or this symbol with a small break in the line )
o ( but it should be filled in )
[] ( should be a hollow square )
/\ ( upside down "V" )
o ( hollow circle )
\/ ( right side up "V" )
- ( thick, elongated dash )
\/ ( with a curved line through the top, like an upside down "A".)
Equiptemperature implies all snow is at the same temperature which is rare in alpine snow.
All metamorphism happens under a temperature gradient of some magnitude. With respect to crystal shape this term is not specific enough since it basically refers to all crystals.
Depth hoar
They have been growing the longest, under warm temperatures and higher supersaturation than crystals elsewhere in the snowpack.

Growth Of Crystals Around Crusts In Dry Snow

Provides a barrier for vapor transport.
Weak bonding of snow above or below the crust.
Vapor transport is prevented, which provides a relatively high level of supersaturation for rapid crystal growth.
Dry on wet snowfall combinations involve "dry" snow falling on "wet" snow. Latent heat in the water fosters a temperature gradient.

Bond Formation In Dry Alpine Snow

Formation of bonds is also referred to as sintering.
Diffusion of water vapor through pore space and molecular motion at grain boundaries.
At grain boundaries where crystals touch.
Grain boundary groove.
Generally from the perspective of ice spheres with a boundary where the spheres touch.
145 degrees
False
Highest stress is found on the interior of the grain boundary groove.
Bond formation is initially quite fast, slowing gradually as time passes.
Differences in crystal size ( mismatch ) result in poor bond formation.
Thermodynamic processes occur faster at higher temperatures. Thermodynamic processes occur more slowly at lower temperatures.
-5 degrees Celsius
A mobile, liquid-like layer that thickens as temperature increases.
When the temperature gradient is high, mass transport is rapid.
Vapor molecules are not longer preferentially deposited at necks and growth occurs on sides and corners of crystals.
Travel in continental climates would be extremely dangerous.
Avalanches are not easily released on depth hoar because of its depth below the surface.
Instability
Large grains have fewer bonds per unit volume; smaller grains have more bonds per unit volume because of tighter packing.
Similar geometry / crystal grain type/size.
Differences in degree of riming can inhibit bond formation.
These crystals pack very tightly and bond very well. This is how slabs form.
List of integrated elements:
- Temperature
- Temperature gradient
- Applied load
- Pore-space configuration
- Crystal type/size
- Interface geometry
About 100 times individual bond size.
The individual bonds don't matter as much.
High temperature and load work together to increase fracture toughness.
Bonding and strength increase slowly for persistent forms because of large grain size, loose packing, and resistance to strength increases from overburden due to anisotropy.
False
In near surface snow. Depth hoar is the exception.
Weak bonding between layers may be more important than low strength in a weak layer.
Shear quality.

Persistent And Non-Persistent Weak-Layer Forms

Canadian researcher Bruce Jamieson.
Anisotropic: weaker in shear than compression, low-fracture toughness, may persistent for long periods of time.
Fracture toughness and bonding increase fairly rapidly due to overburden slab load and temperature. However instability may persist at temperatures below -5 degrees Celsius.
Human perception is poorer because of forgetfulness, spatial variability, or depth of burial.
Human perception is generally good because instabilities are near the surface.
During storms.

Metamorphism Of Wet Snow

Conditions change greatly.
Water, ice, and air.
Smaller particles have a lower melting point than larger particles.

Snow With High Water Content

At 15% water, ice particles may become completely separated from each other.
Heat flux through liquid water.
When all particles are the exact same size.
Heat flux through liquid water is extremely efficient.
Snow with 0% water content by volume.
Snow with < 3% water content by volume.
Snow with 3-8% water content by volume.
Snow with 8-15% water content by volume.
Snow with > 15% water content by volume.
This is another term for wet snow.
This is another term for very wet snow.

Snow With Low Water Content

8%
Capillary pressure in the pore space.
Liquid water is forced out of the pore space, usually draining down.
Grain clustering that occurs as a result of surface tension.
Surface tension of water between grains.
Take its temperature, examine it with a lens, squeeze a handful.
Dielectric measuring device.
Grain growth increases because heat transfer through water is efficient.

Classification Of Wet Snow

No. The snow is still faceted because that is the actual grain type by morphological classification.

Bond Melting And Formation In Wet Snow

Water
The melting point decreases as area of contact increases.
During the day, snow melts, producing liquid water. At night, snow freezes. ( Diurnal temperature fluctuations. ) After several repetitions, the result is large grain sizes that lose most of their cohesion when wet.
Corn snow
A melt-freeze crust can serve as a future sliding layer if buried. A wet melt-freeze crust can produce wet/loose avalanches.

Living In The Moment

2010-11-24T18:46:00.000-08:00

It was a long and dark December, from the rooftops I remember there was snow—Coldplay

NOTE: This is the second post that will address the general question of Why Is It So Complicated? This time we're going to talk about cold weather, avalanche forecasting, and persistent weak layers. Instead of engaging in endless speculation over the state of the winter snowpack, I'd like to take this opportunity to discuss the basic elements of forecasting, and what you can and cannot accomplish with forecasting.

Seeing The Future
Recently there have been a few online discussions about snow and weather conditions in the Pacific Northwest. With the current cold weather, and a generally colder winter forecast, a lot of people are wondering if persistent weaknesses will plague the snowpack this winter.

The straight answer to the above question is as follows: no one really knows what will happen in the Cascades this winter. What we know right now is that the current cold temperatures are almost certainly producing instability wherever the snowpack is shallow, and there is a high likelihood that the cold temperatures are producing surface instability in areas where the snowpack is relatively deep. It is very likely that faceting is widespread during clear, cold nights when the snow loses heat through long wave radiation loss. On solar aspects at high elevations, you might find radiation recrystallisation.

Armed with the knowledge that instability is developing in the snowpack, we can start to speculate about what might happen next.

In some areas, the instability may persist through the next couple of storm cycles, whereas in other areas, the first big avalanche cycle will clean things up. There's also the spectre of a pineapple express, which would produce widespread instability in many places, but not everywhere, while simultaneously producing a fantastic layer of "glue" to heal surface instabilities. On the other hand, a strong rain event could melt the facets and turn the snowpack into a layer of bulletproof concrete.

Of course, in the event any faceted snow is buried to a depth of about 1 metre, the existence of moderate temperatures would allow rounding to prevail in the snowpack...effectively healing instability in areas with deep snow cover. It could take a week in some areas, a couple of weeks in other areas, and in some areas the problem could indeed persist for the entire winter.

When you get down to it, just about anything could happen at this point.

Why Is It So Complicated?
In simple terms, it's complicated because no one knows the future interactions between terrain, snowpack, and weather. Therefore, no one knows whether or not persistent weaknesses will develop. As I often write on this blog, the chaotic interaction between terrain, snowpack, and weather is responsible for much of the uncertainty in backcountry avalanche forecasting. Rich Marriot writes, how can you forecast avalanches if you can't forecast the weather. The short answer is that you definitely can forecast avalanches, you just can't forecast avalanches very far into the future.

So, if the chaotic interaction between terrain, snowpack, and weather is responsible for a lot of uncertainty, it might be useful to understand why this is the case. To do this, we have to examine the discipline of forecasting. In the context of avalanche forecasting, wanting to know why there is so much uncertainty leads us directly to the following principles:

Information Types & Relation to Perception
Scales in Space and Time

These are two of the Elements of Applied Avalanche Forecasting discussed in The Avalanche Handbook. We'll discuss them next. ( Please see The Avalanche Handbook for a complete discussion of these elements. It is dangerous to issue avalanche forecasts using these elements by themselves. )

Why Forecasting Is Difficult
Forecasting is concerned with producing an accurate picture of future events. For avalanches, we can consider information types such as Class I data, Class II data, and Class III data. We can also consider the relationship between perception and data from a specific class. To define the scope of the problem, we can consider scales of space and time, or in very simple terms, we want to know where ( space ) and when ( time ).

To issue any type of forecast, you start by gathering data, and then you subject this information to some form of analysis. If you happen to be out in the backcountry on a particular afternoon, you have the tremendous luxury of hindsight made available by knowing the previous weather, and by knowing something about the current mechanical structure of the snowpack. You can also make very specific observations of the environment, including observations of the terrain and current snow deposition patterns.

On our theoretical afternoon, you also know the current weather. So while it is generally more difficult to issue a precise forecast, you also just happen to have access to an incredible amount of information on which to base any such forecast. To make things even easier, you're only concerned with issuing a forecast for a very short time, and for a very limited number of places. On the other hand, long-range forecasts are based on theoretical weather data ( Class III ), and there is always high uncertainty associated with such data. High uncertainty means that you're much more likely to make errors and blow the forecast as result.

For this reason, forecasts for the immediate time frame and for a small geographic area, often called nowcasts, are the most accurate. A forecast for a few days ahead is less accurate, and a long-range forecast might not be accurate in any sense. Nowcasts are more accurate because uncertainty is lower when we actually know something about the variables affecting the current situation. Unfortunately, we usually can't know the variables that will create or affect situations in the future.

This means that for any date far enough in the future, for a large area, uncertainty is essentially unlimited. If you want to see how this works, issue a forecast for your life over the next minute. What about a forecast for the next hour. What about the next 24 hours. What about next week? What about next month? Three months from now? Three years from now?

Bayesian Logic
The dynamic, integative process humans that use to conduct avalanche forecasting can be referred to as a Bayesian activity. We say that this process is dynamic, because it is active, and because it changes as information is collected. The process itself is integrative because you must consider the evidence as a whole, rather than as separate pieces. This is reflected by the following formula:

Prior × Likelihood = Posterior ( or, what follows )

If we convert that formula to human-compatible terms, we get the following:

The combination of Past Conditions and Current Conditions = Forecast

If you want to issue a forecast for February 14th, 2011, you'll notice a rather glaring lack of information about conditions leading up to that date. The reason why is obvious: you have no information about terrain, weather, and snowpack for that date because it hasn't happened yet.

The most important characteristics of Bayesian revision is the ability for a single piece of data to change the forecast. That means, you throw out the old forecast as you acquire additional data. If you observe unstable snow, your forecast must change.

Try It Out
Here are some exercises:

Forecast snowpack instability for the Cascade Mountains during winter 2010-2011. ( You can also choose your home mountain range if you don't live in the Cascades. )
Forecast snowpack instability for Phantom Trees backcountry ski run on November 30th, 2010 at 2:30pm. ( You can also choose your own favourite backcountry ski run. )
When you're finished with your forecasts, write a short snippet about which forecast is more precise and why it is more precise.
Remember, it's easy to confuse accuracy with precision, but they are not the same thing at all.

Conclusion
With respect to the Cascades, it seems pretty likely that another big dump will produce significant instability. But such general forecasts are easy to issue because it's well known that large dumps of snow produce significant snowpack instability. When we consider the uncertainty of long range forecasting, it's very easy to see why it's all but impossible to say anything about an entire winter.

As usual, we'll just have to wait and see.

But remember, theoretical avalanches aren't dangerous. It's the real avalanches that you have to watch out for, and real avalanches always happen at a very specific place and time.

Addendum
Regardless of the specific place and time in which you find yourself, Happy Holidays to all my readers.

There Are No Magic Bullets

2010-11-17T12:15:00.000-08:00

Chances are, when said and done, Who'll be the lucky ones, Who make it all the way—Five For Fighting

A complete backcountry safety system uses a mix of elements, including thorough planning, safe travel habits, rescue gear, and good judgment. Using multiple risk management elements allows you to reduce risk in a variety of different places, which is the same as not putting all your eggs in one basket. ( Putting all your eggs in one basket is referred to as risk concentration. )

To this point, many recreational skiers go lite on the trip planning, and by doing so they miss out on important opportunities to reduce risk. Then, perhaps due to poor planning, or lack of skill, the party makes a few poor decisions, which again represent missed opportunities to reduce risk.

As opportunities to manage/reduce risk are discarded, more pressure is put onto the rescue gear component of your backcountry safety system. Unfortunately, the rescue gear component of your backcountry safety system is really only designed to give you a chance at live recovery in the event of a complete burial. Rescue gear is not a comprehensive backcountry safety system.

And it's certainly not a magic bullet.

If you travel somewhere frequently, you may be tempted to avoid planning. But remember, even though the terrain remains the same, both environmental conditions and humans are subject to frequent changes. For this reason, it's a good idea to have a set of stock trip plans that you can pull out and review from the perspective of current conditions.

Human conditions: Are you tired? Maybe a bit hungover? How's your hydration and calorie intake? Are you really jonesing for a fix? What about your friends? Environmental conditions: Is avalanche danger high? What do you think the snowpack is doing on your intended route? What does the public avalanche bulletin have to say?

Conclusion
Three major elements of a complete backcountry safety system:

Planning: Thorough pre-trip analysis of terrain, snowpack, weather, and people involved.
Traveling: Safe travel habits, avalanche forecasting, managing yourself, and good judgment.
Rescue: Beacon, shovel, probe, spotting, searching, extraction.

Dust In The Wind

2010-11-10T15:42:00.000-08:00

All we are is dust in the wind—Kansas

NOTE: This is the first in a series of posts that will address the general question of Why Is It So Complicated? While teaching often involves simplification, it's important to remember that you can also use complexity to teach. Despite conventional wisdom, complexity is not always the enemy of simple, and simplicity does not always improve understanding.

Introduction
Today's post is going to discuss wind loading, more specifically the ins-and-outs of using wind speed and direction to forecast wind loading. The main difficulty in using a simple model, is that the simple model doesn't account for turbulence, and turbulence has an incredible influence on the "patterns" of wind deposited snow.

Video 1. You can't see clear air turbulence, but watch this time-lapse video. The presence of clouds makes the turbulence very easy to see. At about 1 minute, you can watch some backwards loading, where turbulent vortices load a slope that is facing against the wind. This is referred to by the very technical term wind slab where you least expect it.

The public avalanche bulletin often contains a forecast of aspects on which you might expect to find wind loading, but it's important to remember that a.) the public avalanche bulletin covers a very large area, b.) avalanche forecasters have a lot of knowledge about the interaction between terrain and weather, as well as a deep body of experience about a variety of such situations in the past, and c.) they also have access to very sophisticated computer models. Forecasters with years of experience at a specific location will also develop a very good sense of how a specific storm will influence loading in certain areas.

Since most of us normal folks don't have that experience, we need to stick with the tried and true.

Character Of The Data
Wind speed and direction is Class III information, which means there is high uncertainty about its relationship to avalanche formation. High uncertainty exists because there are many ways to interpret the data, and as a result, this data may or may not reveal useful information about instability. This is because the physics behind wind flow are intensely complicated and the specific outcomes are very possibly unknowable.

Prevailing Wind
When we talk about wind, there are two important elements: the prevailing wind and local winds. The prevailing wind is located high above rough mountain terrain, where airflow is unimpeded by obstacles. We can express the prevailing wind with a direction such as north or northwest, and with a speed such as 20 knots. Broadly, the prevailing wind is influenced by horizontal pressure differences and the rotation of air around pressure centres.

An additional complication of using prevailing wind is that the varying shape and behaviour of cyclonic weather systems means that the prevailing wind speed and direction can change during the passage of a storm, and it can be difficult to predict these changes because of the dynamic nature of weather systems. The reality is that each storm is a completely unique event that is driven by a set of completely unique parameters that will never happen again. Once you start to understand the complexity, it becomes easier to understand how to use this complexity to your advantage during the process of backcountry avalanche forecasting.

As usual, this complexity provides very useful clues about what not to do.

Local Wind
Anyway, things become awfully complicated when a large storm moves over the mountains and the air starts interacting with terrain. This is referred to as local wind. Local wind is formed from a complex stew of frontal lifting, orographic lifting, convective lifting, and convergence-based lifting, in addition to frictional forces.

Picture a mountain valley, along with all its nooks, crannies, and crevices. As air moves through complex mountain terrain, it hits obstacles that cause it to become turbulent. Large features block and channel the large scale flow, while airflow over, around, and through smaller barriers generates localised turbulence. On this blog I frequently refer to the chaotic interaction between terrain and weather, and these crazy wind patterns are a very large part of the chaos. Naturally, the mere presence of chaos raises uncertainty because chaos suggests that uncertainty is the only state of affairs.

Clouds, along with other sophisticated meteorological data, can provide a fairly good visual model of this turbulence at a large scale, but these data are almost no use at the small scales required for effective backcountry avalanche forecasting. At small scales, we can use weather stations to measure local wind, but because of resource limitations, our picture of local wind speed and direction is actually extremely limited.

Thankfully, despite these problems, there are a few really good techniques that we can use to determine if wind loading has occurred. In simple terms, even though the wind is invisible, and even though the chaos of turbulence makes it very hard to determine local wind flow, we can observe the physical environment for the signals of wind loading.

Examples
What do we know about the complexity of wind speed and direction at a single location? What about the chaotic complexity of turbulence?

Figure 1.1. Wind speed and direction at 1 hour increments for Crystal Mountain "Green Valley" weather station over the course of a single day. Since the weather station measures wind on an hourly basis, there is a lot of missing data here.

Figure 1.2. Wind speed and direction at 1 hour increments for Crystal Mountain "Green Valley" weather station over the course of a single day. Here, the pattern matching software in our brains sees two broad patterns that may be associated with a major wind direction change that occurs when a cyclonic weather system passes over the weather station. Or, maybe our brains are seeing a pattern where no pattern exists.

Figure 1.3. Wind speed and direction at 1 hour increments for Crystal Mountain "Green Valley" weather station over the course of a single day. Here our brain is tempted to view "clusters" of wind directions, but even if these "clusters" do occur, our brain is simply incapable of accounting for turbulence, and these "patterns" may very well arise from turbulence and contribute to additional turbulence. It's pretty crazy, isn't it?

Figure 1.4. Complex deposition and drift patterns near the toe of the Sulphide Glacier. Can you identify the wind slab? Does the wind slab have a simple shape? Is the layering simple or complicated?

Figure 1.5. How complicated is turbulence? I'll engage in a gross oversimplification, but you can clearly see the vortex generation that is one of the hallmarks of turbulent fluids such as air. In the mountains, this effect produces cornices in some situations, and in general it produces loading patterns that are incredibly intricate. These loading patterns produce wind slabs of varying size and depth. The depth of a wind slab often varies greatly across a very small area, which further raises uncertainty about the likelihood of avalanche formation.

Figure 1.6. From MIT. The difference between laminar and turbulent flow. Imagine this in three dimensions, and then imagine trying to relate this model to snow deposition patterns. By now it's pretty obvious that you can't actually do this. It's worth mentioning that a supercomputer with 1024 cores might be able to produce a relatively accurate simulation. However, small inaccuracies in the input data, including inaccuracies that are immeasurably small, and/or inaccuracies in the mathematics of the simulation, will produce severe errors at every scale. This means that you'll end up with a simulation that "looks accurate", but actually has no relationship to the real world.

Conclusion
So what's a guy or gal to do? Well, given the complexity and uncertainty that arises, observations of local weather and snow deposition patterns remain the gold standard for discerning the parameters of wind loading. You can safely assume that any combination of wind and snow means that some wind loading has occurred.

Significant amounts of snow are removed from windward slopes.
Significant amounts of snow can be deposited on lee slopes.
Drifting patterns. Drifts point in the same direction as airflow.
Snow build up, or the lack thereof, on trees and rocks.
Cornices point in the direction of airflow and indicate loading below.
Look for ripple patterns on the snow surface.
Observe the snow's texture, especially its hardness.
Wind slab often sounds hollow when you step on it.
Wind slab has an intricate shape and layering.
Complex stratigraphy raises uncertainty.
Delicate and/or intricate transitions between clean and dirty snow may exist.
Given the foregoing, never try to outsmart the snowpack. It simply can't be done.

Obviously, there's a theme: stick with tried and true methods of using visual observations to assess wind loading. These methods are far better than trying to model wind loading by using the prevailing wind direction.

Futher reading that merely hints at the unreal complexity of the problem:

Chaos Theory ( Wikipedia )
Turbulence ( Wikipedia )
Navier-Stokes Equations ( Wikipedia )
Wind Tunnels ( Wikipedia )

Great Learning Resources

2010-11-05T17:09:00.000-07:00

We Don't Need No Education—Pink Floyd

Here are two absolutely wonderful resources. Free registration required.

Learn about snowpack: http://www.meted.ucar.edu/afwa/snowpack/

Learn about avalanche weather: http://www.meted.ucar.edu/afwa/avalanche/index.htm

New From The Canadian Avalanche Centre

2010-10-28T06:29:00.000-07:00

What we see and what we feel—Jonsi

The Canadian Avalanche Centre has published a great guide for advanced recreational skiers:

http://www.avalanche.ca/cac/pre-trip-planning/decisionmaking

Avaluator 2.0 is also available:

http://www.avalanche.ca/cac/store/books

Trip planning form:

http://www.avalanche.ca/resources/cac/attachments/trip-plan-form

These are great products from a wonderful organisation.

Union Creek

2010-10-22T21:53:00.000-07:00

I keep dreamin', you'll be with me and you'll never go—Nickelback

This post is in memory of Kevin Carter, Devlin Williams, and Phillip Hollins.

February 2008
Almost three years ago I sat in a Seattle coffee shop and read an article in The Stranger. The sharp words pricked a nice hole in the warm bubble of what was an otherwise quiet afternoon: three snowboarders disappeared in Union Creek during early December, and they had not been seen, nor heard from since.

It was a La Nina winter, and you can bet snow was on my mind: I'd already visited friends in Revelstoke once during early January, and my upcoming travel plans included another trip to Revelstoke, followed by a trip to Banff to see my aunt and uncle.

So, I won't really get into what was going on in my life at that time, but I think massive changes sums it up quite nicely. In the past three months I had finally started to escape from a very dark hole, and I wanted nothing more than to stay in British Columbia and spend the rest of the winter climbing my way out of the awful black.

Not yet ready to head back to the States, I extended my trip and spent some time skiing near Valhalla Provincial Park. Sitting alone in my hotel room one evening, I realised that computer graphics techniques already provided solutions to the certain types of perception problems. We look at maps, and we get an idea about where we should and should not travel in general. But the computer can transform a map from merely useful to truly useful.

Theory of Relativity
In addition to incredible ease of access, the backcountry near Crystal Mountain is middle ground terrain. This sets up a classic middle ground perception problem because Union Creek has a rather benign appearance relative to high alpine terrain. In other words, you can drive to the trailhead, skin from the car, but you won't see enormous snowfields below savage peaks. Instead, as mountain terrain goes, Union Peak is really sort of small, steepish, and extensively gladed. To this point, there are plenty of places that seem safe..

In a typical scenario, the skier examines the choices in front of them and selects what 'appears' to be a safer option. A common equation is as follows: trading steepness for trees, or trading open slopes for tree covered slopes. However, safety is relative, and safer is not the same thing as safe. When avalanche danger is High, statistically speaking, the safer option might not actually be any safer at all. Without hard numbers, how do you know if you're really reducing or exposure or if you're just trading horses?

Can you identify ski runs that are safe during high avalanche danger?

You can examine the terrain from the air, and can you stare at contour maps all day long, but the fact of the matter is that the human mind just isn't very good at certain types of tasks. Computers are wonderful tools, and they are quite happy to help us cut through the clutter of our minds and tell us the truth.

Want to take a look at what the computer sees?

Union Creek

Union Creek is popular backcountry terrain east of Crystal Mountain Ski Resort. Union Creek contains COMPLEX avalanche terrain. In poor conditions, line-of-sight is limited and safe travel may be difficult for anyone regardless of skill level. Start zones in Union Creek are capable of producing large, destructive avalanches.

Required Skills: Expert route finding and expert snow stability assessment.

Visualization of terrain > 25 degrees and < 25 degrees. Avalanches often run into blue terrain.

Avalanche Terrain!

Terrain Trap!

Elements of avalanche terrain at Union Creek.

Element	Exposure
History	People have been killed by avalanches in Union Creek. Large soft-slab avalanches run during and after storms. Surface hoar formation is widespread in this drainage. Faceted snow often develops near ridgeline and rocks. Wind-loading occurs during high winds. Local skiers report 1, 2, and 3 foot crowns. ( Crown size of 30cm to 1m. )
Avalanche Starting Zones	Multiple avalanche starting zones are found below ridgelines.
Avalanche Paths	Channeled and unconfined avalanche tracks are found throughout Union Creek. Avalanches move very quickly in confined tracks. On the east and north slopes, several large, poorly defined paths exist below large, open start zones. Numerous, small avalanche paths run through trees on all the slopes of Union Creek. Avalanches in these narrow, tree-lined paths are extremely dangerous.
Avalanche Runout Zones	A network of gullies forms overlapping runout zones at the bottom of Union Creek. This region is a complex, dangerous terrain trap. Other runout zones extend into forested areas.
Shape	Convoluted, with very frequent changes between concave and convex slope shapes.
Large Surface Area	Terrain in this drainage has a very large surface relative to its size on a map. Large amounts of snow accumulate throughout Union Creek.
Steep Terrain	Much of the terrain in Union Creek is very steep and avalanche prone. In many areas, more than 90% of the terrain suitable for skiing is between 30-40 degrees.
Open Terrain	Union Creek has large areas of open terrain.
ConfinedTerrain	Some locations in Union Creek feature highly enclosed terrain.
Line-Of-Sight	Some locations in Union Creek have limited line-of-sight. You may not be able to see overhead avalanche terrain because of terrain features or trees.
Terrain Traps	Union Creek has numerous terrain traps such as convexities, trees, depressions, and gullies. Computer modeling finds hundreds of terrain traps.
Safe Areas	Ridge areas are safest. Terrain on the valley floor, if below open terrain above, is not safe. Many of the avalanche paths in Union Creek are enlarging every winter. There are safer areas in the valley below thick expanses of trees that run to the ridgeline.
Exposure Time	Many ski runs and travel routes are exposed to avalanches for their entire length and offer no chance to reduce exposure. Less dangerous routes do exist, but require expert route-finding relative to the current conditions. Deep snow and steep terrain often make uphill travel slow and difficult.

Dancing Around Uncertainty

2010-10-19T23:40:00.000-07:00

But it's one missed step ... one slip before you know it—Sarah McLachlan

There is an interesting article on Friends of Berthoud Pass web site.

Our Friend Bob Berwyn at the Summit County Voice wrote recently about the growing need for basic avalanche awareness among “sidecountry” skiers in Colorado.

Avalanche awareness programmes are wonderful, but many of them do not present balanced thinking frames for beginner recreationists. Programmes that focus entirely on "avalanche awareness" do so at the expense of "avalanche uncertainty", which leaves students with only half the mental model that they need to make good decisions.

The winter snowpack is conditionally unstable, and very often this means that it can be difficult to determine the extent of instability and its parameters. Of course, this is often the point where human nature steps in and people find their own ways 'manage' the uncertainty.

Failing to proactively manage uncertainty is at the root of many avalanche accidents for the following reason: a highly uncertain mind is very susceptible to biases, speculation, rationalisation, and the disregarding of facts.

Since some degree of residual uncertainty always remains, and since the degree of uncertainty is often inversely proportional to the skill of the recreationist, it seems strange to focus so much effort on awareness without addressing the other side of the coin as well.

We've all seen this take place during online discussions, at avalanche awareness events and during level 1 classes. Someone asks a question and the instructor provides additional information along with a qualification or two. This leads to additional questions and qualifications, as the instructor and students dance around the uncertainty.

I believe avalanche awareness programmes and level 1 classes must explicitly address uncertainty and teach students that decisions should retain a conservative character when their uncertainty is high. This would present a much more balanced mental model to beginners, and it would also help smooth out the cognitive dissonance that arises when observations of the terrain, snowpack, and weather don't provide clear answers.

Further Reading

Q & A: La Nina

2010-10-13T16:48:00.000-07:00

Look around, leaves are brown, There's a patch of snow on the ground... - Simon & Garfunkel

Several people have emailed me questions about La Nina in the last couple weeks. The general vibe: people want to know what a La Nina winter will mean for avalanche safety in Washington State.

From a meteorological perspective, a La Nina winter is colder and wetter, which means larger, more frequent storms, and lots of snow in the mountains. However, La Nina has no mysterious influence on the snowpack itself. Prolonged cold temperatures, which can occur during any winter, will either produce new snowpack instability or allow existing snowpack instability to linger for longer periods of time. Large storms, which can occur during any winter, always produce instability. Rising temperatures during storms always produces instability. Some or all of these events may happen more often in a La Nina winter, but the snow safety rulebook won't change. You can learn more details about La Nina years on Amar Andalkar's excellent web site.

What about avalanches during La Nina winters? The last La Nina winter was 2007-2008, and there were a record number of fatalities in Washington State. For example: there were 5 fatalities in Washington State during a single weekend in early December 2007. In North America, there were 14 fatalities during the month December. That's basically one fatality every other day.

So, where were we? ...Frequent storms and lots of snow in the mountains... Sounds perfect, right?

Yeah, it's perfect ... but like everything wonderful, there's a catch. According to The Avalanche Handbook, "direct loading by synoptic scale weather events causes most avalanches". In other words, lots of storms means lots of potential for skier-triggered avalanches. Avalanches that occur during storms are referred to as direct-action avalanches, and these avalanches occur during a storm or within 24-72 hours after the storm ends. It's a good bet that public avalanche bulletins in North America will often forecast High avalanche danger during the upcoming winter.

What's your strategy for touring on days when avalanche danger is High? Do you have a list of trips for different levels of avalanche danger? ( Feel free to post tips in the comment box. )

The Take-Away

There will be frequent storms.
Avalanche danger will be High during and after these storms.
Start thinking about terrain choices for the winter.
Always choose terrain appropriate for current conditions.
Develop a list of "go to" terrain that is appropriate for high avalanche danger.
Plan like your life depends on it. ( Because it might. )
Take an avalanche safety course if you haven't already done so. United States / Canada
Hire a guide for big trips.

Mind Games

2010-10-02T15:23:00.000-07:00

We're playing those mind games together, pushing the barrier-John Lennon

In my last post, I remarked on an avalanche described in Backcountry Magazine. As promised, here is some discussion that skips the armchair quarterbacking.

Background
Conditions on the day of their ski tour were as follows: a snowpack with a history deep instability had been very recently loaded by rain that was followed by 18 inches of snow. Obviously, even a cursory evaluation of conditions on the day of the tour should have raised awareness about the presence of instability. That aside, if the potential for high instability wasn't obvious from the recent weather and the history of the snowpack, the results of an extended-column test performed by the skiers ( ECT 5 Q2 ) should have been conclusive.

Yet despite the history of the snowpack, and despite the recent loading, and despite snowpack tests, all of which pointed to widespread instability with low triggering energy, the group ventured toward avalanche terrain and triggered an avalanche large enough to bury, injure, or kill a person. Thankfully, no one was injured.

From reading the article, and from examining their terrain choices, it seems as if the skiers were confused and uncertain about instability. Yet the manner in which I have laid out the facts about conditions leaves absolutely no question about the presence and parameters of snowpack instability on the day of the avalanche. So, as with all forms of armchair quarterbacking, in hindsight the snowpack instability seems perfectly obvious...

Clearly something doesn't add up.

Analysis
Armchair quarterbacking is linked to the old saw: hindsight is 20/20. Therefore, when analysing accidents, it's critically important to ask the right questions: Do we really know if the skiers collected information in the same manner as us? What I mean is, did the skiers systematically collect and integrate information about conditions on the day of the ski tour? The article makes it pretty clear that the skiers collected information, but we do not know if they did so systematically, and despite being 'experienced', they clearly did a very poor job of integrating the information into their forecast. Did the skiers even develop an avalanche forecast? We don't know, but it isn't mentioned in the article.

Unfortunately, 'experienced' backcountry skiers frequently make dangerous mistakes, and the reasons why 'experienced skiers' make serious mistakes is a subject of much discussion in the avalanche research community. The magazine article chalks the errors up to powder fever and human factors, but I think both of these are just red herrings. Uncovering the actual mistake is important if we want answers that are clear and useful. Powder fever is certainly dangerous, but repeating that message doesn't really help anyone when powder fever is not the underlying cause. ( In medicine, fever is a symptom that reflects an underlying condition. ) Careless oversimplification greatly reduces the value of discussing skier-triggered avalanches.

After reading the description of their ski tour and the avalanche, the fundamental mistakes became very clear: the ski tour was a somewhat organic, loose, and chaotic endeavour on a day when avalanche danger was high. The presence of chaos is an extremely important clue, because it reveals what really went wrong. Just think about it for a moment .... a chaotic ski tour ... poor choice of objective ... on a day when avalanche danger was high ...

In this case, hopefully we can agree that 'experienced' refers to a person who has engaged in several seasons of ski touring. Hopefully we can also agree that there is a relationship between skill and experience, but that being experienced is not the same as being skilled.

What would lead a party of 'experienced' backcountry skiers down the garden path?

Lack Of Planning: A Fundamental Error
At the beginning of this post I stated that snowpack instability was glaringly obvious when in hindsight we systematically collected and integrated information. Armchair quarterbacking is so easy precisely because it's very simple to systematically collect and integrate information after the fact. But if you're a backcountry skier, it's incredibly important to systematically collect and integrate information before, during, and after a ski tour.

Of course, the systematic collection and integration of information has important implications, doesn't it? And what might those be? Is it possible that the systematic collection and integration of information occurs only when a ski tour is properly planned and properly executed? What are the odds of properly executing a ski tour when the trip has been poorly planned? The article content makes it quite clear that the ski tour was chaotic. So, even if there was some degree of planning, the planning certainly wasn't done properly. Second, the ski tour was executed in a rather haphazard fashion.

We know that a variety of activities such as map reading, instability tests, and route-finding took place on the day of the ski tour. That these activities had taken place obviously lead the participants to believe that their ski tour was properly planned. Yet none of the skiers discuss a formal trip plan, and this leads me to conclude that their tour was not properly planned, but merely discussed instead. Poor planning allowed 'powder fever' and 'poor communication' to take control of the situation. It's very simple: if you don't take control of the situation, something will, and this is doubly true for situations where uncertainty is high. ( I've written about the effects of unmanaged uncertainty. )

The article describes the skiers as experienced. Yes, there's that ugly word again. Since when did experience serve as a substitute for proper planning and execution? Please allow me be perfectly clear: discussions are not planning and experience does not guarantee clean execution. Rather than chalking up another series of mistakes to 'powder fever', it is more useful to consider how and why the circumstances developed in the first place.

Planning is a reality check that you can't afford to miss. If you don't plan, you're being intrinsically careless. If you don't plan properly, you're not planning. If you plan and execute poorly, you fail. Most of the time, failing to plan and poor execution won't have any consequences.

Most of the time.

Conclusion
Failing to plan is a serious primary error that creates situations in which secondary errors will occur. Rather than focusing on becoming an experienced backcountry skier, choose to become a skilled backcountry skier instead.

A Formula For Winter 2010-2010:

Solve for PYST, where = P = Plan, Y = Your, S = Ski, T = Tours

Planning Tips
Here are some planning resources:

Google Maps ( Select More » Terrain for online contour maps. )
Backcountry Skiing: Skills For Ski Touring & Ski Mountaineering
Washington Terrain Ratings ( From This Blog )
Elements of Backcountry Avalanche Forecasting ( From This Blog )

Planning Checklist
Here is a planning checklist:

What is the current danger level?
Who is going?
What are their phone numbers?
What is their contact info?
Is our objective appropriate for the current danger level?
Do we have powder fever?
Have I planned the trip?
Do I have a map?
Have I analysed the terrain beforehand?
Do I have a list of safe alternates?
Have I separated the trip into legs with times, distances, and elevations?

Ex Posto Facto

2010-10-01T18:22:00.000-07:00

Interesting article in Backcountry Magazine. I'll spare you the armchair quarterbacking, but the pictures and accompany text tell a very interesting tale. There were several key mistakes made. I'll write a full post - sans quarterbacking - once I read the entire article.

Fantastic Map Link

2010-09-04T10:21:00.000-07:00

I'm big on planning, and here's a great mapping product:

http://mapper.acme.com/

VirtualMountains

2010-09-03T09:14:00.000-07:00

Hey Everyone,

Hope your summer has been fun. I've been awfully busy traveling and working.

Anyway, let's open up the season with a link...

http://www.virtualmountains.ca/

Like you, I'm looking forward to a LONG and SNOWY winter.

Happy Trails

2010-04-12T14:58:00.000-07:00

I hope everyone has enjoyed this blog for the 2009-2010 season. This blog is going on hiatus until ISSW 2010, during which I will begin posting again.

Please have a happy, fun, and safe spring touring season.

Best,

Mike

Trip Planning

2010-04-04T17:50:00.000-07:00

Mistakes have been made that left me crashing through the ice—Casey Stratton

NOTE: This post contains an entirely non-commercial, completely unsponsored link to Amazon.com.

One important difference between professional guides and recreational skiers is the level of planning that goes into each tour. Professional guides are usually well-versed in the snowpack history for the current winter, and have access to a lot more information than the average backcountry skier.

Touring during high avalanche danger is a complex risk-management problem that requires professional conduct, including planning and excellent judgment. Diligent planning can raise awareness and help minimise uncertainty before you even hit the backcountry.

How can you manage the risks?

Remember, the fastest way to find yourself in the middle of a disaster is to travel somewhere you don't belong. So, with that in mind, it's best to start small ... very small.

Why Plan?
Planning is a great way to stay alive on backcountry outings that take place during high avalanche danger. The best ski days usually take place during high avalanche danger, so having a good plan enables you to make optimal terrain and slope choices. It's a bit heretical to suggest that backcountry skiers can ski safely during high avalanche danger, but it is possible. It is definitely not a good idea to go backcountry skiing during high avalanche danger if you can't be bothered to spend a few hours planning. In other words, if you're not willing to plan, then don't go touring during high avalanche danger because, as a danger to others, you simply don't belong in the backcountry.

At the recreational level, planning for a day tour often involves little more than selecting an appropriate area and finding a trailhead. It's really quite easy if you have prior experience in the terrain, or if you are comfortable playing by ear. With some education, experience, and common sense, using an informal process is probably safe on days when avalanche danger is low or moderate.

Touring during high avalanche danger is only possible with flawless route finding, careful slope selection, and an accurate assessment of current instability. For example, conventional wisdom says that you should avoid touring in avalanche terrain during high danger, or you should stick to the trees. The only problem is that avoiding travel in avalanche terrain during high danger is fundamentally incompatible with how most ski touring takes place, and the trees are a terrible place to be during an avalanche.

Heliotrope Ridge
I recently went on a trip to Heliotrope Ridge, and having never been there before, I actually planned the trip because I had no experience with the area. For those who are unfamiliar with Heliotrope Ridge, it's a fantastic area with incredibly beautiful, fun terrain. One of my partners discussed heading up Grouse Creek, so I decided to examine the terrain using a contour map of the area made available at Google Maps. This is a great resource because the shaded view makes it much easier to read the terrain than a standard contour map. On the other hand, it's not nearly as detailed as a Natural Resources Canada quadrangle or USGS quad, so keep that in mind.

Avalanche Characteristics Of The Terrain
Figure 1.1. Heliotrope Ridge Contour Map. Grouse Creek is clearly shown in the left side of the image.

Blue line indicates route of ascent.
Red areas indicate avalanche starting zones.
There is a small series of moraines that serve as flow retarders.
These moraines are also capable of redirecting flow away from a steep section of our ascent route.
These moraines would NOT provide any protection from a large, dry avalanche.
In general, FEW options to reduce exposure along this travel route.
Terrain is COMPLEX.

This means that our route of ascent, which included travel through an obvious terrain trap / line-of-flow was somewhat protected from the large starting zone above the gully. When I say line-of-flow, I am referring to the fact that a channel such as a gully is a location where you expect to find very fast moving avalanches. Why analyse terrain for large, natural avalanches? Well, natural avalanches are a concern if you're touring during high avalanche danger. So, examine the contour map, and satellite imagery, and start thinking like an avalanche. Where would you start? Where would you flow? What would you hit on the way down? Where would you stop?

Figure 1.1. Heliotrope Ridge Contour Map. This provides a view of the terrain contours with helpful shading.

Figure 1.2. Heliotrope Ridge Satellite Map. The aerial imagery option provides additional details.

Analysis:

Grouse Creek is basically a large avalanche path fed by multiple starting zones.
The path produces very large avalanches capable of tearing mature timber to the ground.
From an aerial study, it's not easy to determine which type of avalanche caused the destruction.
However, once we were on-site we observed:

Chaotic distribution of destruction.
Obvious damage high up on some trees.
Damage in unusual places, such as UPHILL from obvious starting zones.

This clearly showed that large dry avalanches, which can take unpredictable paths, were responsible for most of the damage.
The powder component of a dry avalanche ( 90 mph winds laden with snow )often snaps the upper part of the tree even if the flowing core of the avalanche does not reach the trees.
Wet avalanches tend to move much more slowly and follow the terrain.
Wet avalanches tend to break the trees right off at the base.
However, there were two levels of tree growth: old growth and ~10-year growth. This further convinced me that large, full-path avalanches were not frequent events.
Areas with infrequent LARGE avalanches are almost always beset by many small avalanches over the course of a season. These small events may not leave many visible marks, but rest assured, they do occur.
We were going to travel in terrain where Size 2 and Size 2.5 avalanches are fairly frequent.

In any case, there hadn't been enough recent precipitation for large, dry avalanches, so I wasn't particularly concerned. On the other hand, large accumulations of precipitation at the start of the tour, evidenced by deep ski penetration for example, would have been an immediate red flag. I probably would have turned around or found another way up.

The Trip Plan
After an hour or two, I had a pretty good idea of the character of the trip. We planned to approach through obstacle-filled terrain from the bottom, and there was a lot of overhead avalanche terrain, with many limitations to line-of-sight. ( Does this sound like good judgment to you? ) In this case, a lot of precipitation would be an immediate red flag. I didn't plan an alternate route, but knew that one existed up through the thick trees between our planned ascent route and our planned descent routes.

Option A. Mt. Baker Summit. Not realistic, but it was discussed. No one really wanted
to carry an additional 20 lbs of mountaineering gear.
Option B. Coleman-Deming Saddle. We discussed this option, but upon seeing fantastic
powder conditions, and NOT having any glacier travel gear, we decided against it.
Option C. Ski Bump. We chose this option and enjoyed about 3000 vertical feet of
powder turns.
Bands. All three tours involve travel through all three elevation bands. Below-treeline, At-Treeline, and Alpine.
Leg 1
- Start of Grouse Creek Avalanche Path 3600 ft
- Entrance of Moraine Gullies @ 4800 ft
- 1200 vertical ft
- Band: Below-Treeline
- Notes
  - Travel to entrance of moraine gullies and take a left.
  - This route is exposed to overhead avalanche terrain.
  - This route travels through confined terrain with limited line-of-sight.
  - This route is exposed to three avalanche starting zones.
  - This route travels through an obstacle-filled debris accumulation zone.
  - At least one of the starting zones is partially obstructed by moraines.
  - The start zone at top, skier's right is very large and probably responsible for the largest avalanches.
Leg 2
- Entrance to moraine gullies 4800 ft.
- Notch below "ski bump" @ 6400 ft.
- 1600 vertical ft.
- Band: At-Treeline, Alpine
- Notes
  - Climb up and left toward notch.
  - This route is exposed to overhead avalanche terrain.
  - This route travels through confined terrain with limited line-of-sight.
  - A series of moraine features provide some protection.
  - These features can retard some flowing snow.
  - These features can re-direct some flowing snow away from travel route.
Leg 3
- Notch below "ski bump" @6400 ft
- Top of "ski bump" @7100 ft
- 700 vertical ft.
- Band: Alpine
- Notes
  - Climb slightly skier's left to avoid being taken into gully in case of avalanche.
  - Prospects for rescue are "simpler" on skier's left.
  - Main Reason: Good line-of-sight, simple slope shapes.
  - However, there are a few places with potential for deep burial.
  - Avalanches don't frequently run the entire length from skier's bump to tree-line.
  - If they did, the destruction would be much larger.

Details, Details, Details
After a few hours of climbing, we arrived at the top and took in the scenery. We then decided to take a 1500 foot run down the clean, safe part of the snowfield. Conditions were great, almost boot-top powder and nearly zero instability. ( A mix of fresh crystals on top of decomposing and fragmented crystals. ) At the bottom of our first run we discussed heading up for another, and began the ascent. During the skin up, a layer of clouds came in and the temperature rose. We discussed conditions during lunch at the ridge. Everyone agreed that stability was good up high, but that the temperatures were becoming a source of concern, and freezing levels were rising. Plus, we were greeted with this view as we stared into the valley:

Ski quality up high was excellent, but after the first run, I was concerned about the layer of clouds. More specifically, I was concerned about the ragged border where the clouds met the mountains. This type of border allows sunlight in, but the thin clouds create a greenhouse effect that prevents cooling. In short, avalanche danger at the region where the clouds met the mountains was almost certainly going to be high. We knew the snowpack ( 6-10 inches of new ) was unconsolidated and unbonded to the old snow below. The small snow depths meant that skier-triggered avalanches were not likely to be dangerous, but we were prepared for instability during the descent. And as it turns out...just below the clouds...

A member of our party triggered a small, thin soft slab avalanche. A bit bigger than Size 1, but probably not enough to bury, injure, or kill a skier. Avalanches are often easily triggered during the process of consolidation, especially if consolidation is very rapid. ( Snow doesn't like rapid change. ) In this case, the snow that avalanched had been powder only hours before. The snow quickly turned to rubbery cement as we descended through the clouds, providing conclusive evidence that the sun was working its magic.

I've worked extremely hard to avoid surprises, and it felt good to issue an accurate avalanche forecast that helped us avoid a nasty surprise. Since I was surprised and partially buried by a similar avalanche in 2008, I'm going to use this avalanche as a reminder that A. ) Education works, B. ) Planning works, and C.) I need to keep learning so I can keep turning.

Notes
DO NOT tour during high avalanche danger if you feel that this level of planning exceeds your knowledge or experience.

Professional-level planning and travel techniques include the following:

Use careful planning to raise awareness and minimise uncertainty prior to the trip.
Do not travel somewhere you don't belong.
Do not travel in unfamiliar terrain during poor visibility.
Evaluate party members, especially individual risk acceptance.
Identify the characteristics of avalanches in the area.
Find additional route options.
Formulate a strategy to ascend safely.
Formulate a strategy to descend safety.
Create a table of vertical/times/distances for the chosen routes.
Take several reconnaisance trips to the area.
Avoid traveling below overhead avalanche terrain.
Avoid cornices, locations suitable for rock fall, and slopes holding loose snow.
Shortcuts kill, so go around if you don't have a heli.
- If you can't go around, go fast.
- If you can't go fast, go to a resort.
Choose slopes where avalanche rescue is possible.
- Descend slopes without obstacles such as trees and rocks.
- Look for smooth, clean runout zones with excellent line-of-sight from the top.
- Poor line-of-sight, such as in trees or convoluted terrain, makes rescue much more difficult.
- Have an escape plan for key components of the line.
Forget about skiing between supposed safe zones.
- There are no safe zones.
- Safe zone prediction often involves foolish assumptions about propagation.
Choose steeper slopes with extreme care, even if the slope is small.
Choose slopes you can ski from the top.
Choose slopes you can ski cut safely.
Pick your line of descent very carefully.

Photos
Here are some photos from the trip.

Further Reading

The Importance Of Considering Natural Avalanches
Although Capable, Guides Should Never Ski Alone
Snowmobilers Raising Cash For Canadian Avalanche Centre
The Avalanche Handbook ( You can learn how to evaluate terrain like a professional. )

Details, Details, Details

2010-03-28T13:15:00.000-07:00

I've seen clouds from both sides now—Joni Mitchell

This is a line from one of my favourite songs. Anyway, I'm not sure if this song is so good because the lyrics are so universally brilliant, or just because Joni is a goddess. The message of the song, just when you think you've got it all figured out..., is very relevant for avalanche safety.

With that in mind, what is wrong with the following picture?

Exposure Is Personal

2010-03-24T18:54:00.000-07:00

We reached the dizzy heights of that dreamed of world—Pink Floyd

NOTE: I updated this post on March 28th, 2010. I don't include the role of avalanche size in the discussion on danger because it is possible to be killed by a very small avalanche.

Often times you hear people discuss "mitigating risk", or "mitigating hazard", and so forth. From these discussions, it's clear that many people can't distinguish between hazard, danger, and risk. ( Which is perfectly understandable since these words are fuzzy and woefully imprecise. )

There is a difference between exposure, danger and risk, and in addition to the differences, it's also very important to understand how these variables interact. Risk is classically defined as chance, consequences, and exposure, but in this post I'm going to explicitly re-fashion the key elements of risk to revolve around your personal risk acceptance level, since the real source of most risk is from within.

Exposure

You are always exposed to avalanches during travel through avalanche terrain—that's why it's called avalanche terrain. Usually during times of high avalanche danger, you can reduce exposure by choosing gentle terrain, or by using very careful route-finding / travel technique when traveling through exposed terrain.

Danger

The actual avalanche danger may be very low or very high. The danger level reflects the likelihood of avalanche formation, as outlined in the public avalanche bulletin, or as judged by your own observations in the backcountry. You cannot modify the current avalanche danger, but through informed terrain choices, you may be able to choose slopes where avalanche danger is lower.

Risk

Your personal risk acceptance level determines your tolerance for exposure and danger, which in turn determines the chance of avalanche involvement and the consequences thereof. This is why avalanche professionals often say most avalanche accidents are the result of choice, not chance. Again, the most important source of risk comes from within.

Scales For Exposure, Danger, And Risk

Figure 1.1. Avalanche danger scale from LOW to EXTREME. This graph shows the likelihood of avalanche formation, and this information is available in the public avalanche bulletin, or formed by your own observations in the field.

Figure 1.2. Terrain Exposure Scale. This graph shows the amount of exposure for a given route or geographic area. One problem is that there are few terrain ratings available for Washington State. ( I've assembled ratings for some popular areas, but the list is still very incomplete. )

Figure 1.3. Risk Acceptance Scale. This graph shows the amount of risk you are willing to tolerate. Baseline risk tolerance varies greatly by individual, and specific individuals have different risk tolerances at different times as well. You may generally accept higher risk, but even this will vary.

Your Personal Exposure Score

Calculate your personal exposure by using the following formula.

risk tolerance + avalanche danger + avalanche exposure = personal exposure score

Avalanche Danger Score: Current danger level, 1-5, multipled by 2.

Considerable = 6.

Terrain Exposure Score: A number from 0 to 10.

0 = no exposure.

Personal Risk Score: A number from 0 to 10.

0 = low risk tolerance.

One of the most important, and least discussed elements of avalanche safety, is the complicated relationship between exposure, danger, and risk, and the process of managing awareness and uncertainty. Reducing exposure commonly makes people feel less uncertain, even though a reduction in exposure may not have the desired effect when you actually want more risk.

Always evaluate the moments when you seek to preserve risk. Often these are moments when we look for something fun, exciting, or notable.

Further Reading

Avalanche Hazard, Danger, And Risk - A Practical Explanation
An Extremely Close Call On Johannesburg Mountain
Repeat after me: "I am the source of risk and danger."

The 7 Deadly Sins

2010-03-18T15:46:00.000-07:00

if I could turn back time—Cher

This list is composed mostly of my own thoughts about what constitutes the seven deadly sins of winter backcountry travel. Your mistakes may differ, and your mileage may vary.

Lack of preparedness.
Failure to maintain awareness.
Failure to manage uncertainty.
Poor communication.
Not paying attention.
Ignoring margin-of-safety.
Failing to reduce expectations.

Feel free to suggest additional mistakes.

Behavioural Strategy

2010-03-17T14:38:00.000-07:00

I can't live, with or without you—U2

I've been busy with job, family, and snow. So I haven't really had a chance to properly finish two posts on which I am currently working. My day job involves business and software, so for the business side of my life, I subscribe to the McKinsey Journal. Today, a very interesting article from their newsletter arrived in my inbox.

It's probably hard to see how a hardcore business journal could have any applicability to backcountry skiing. Yet, after the recent events in British Columbia, I think an article on behavioural strategy is highly appropriate. I had to read the article several times to digest the information, but it's definitely worth the effort. The article touches on some topics that will be familiar to most people who have studied avalanche accidents: why do people make such poor decisions in the face of hard evidence? And why does it happen ... again and again and again?

The article also discusses the importance of the process used to make decisions, which for many recreationists is not formalised. Information from the article dovetails nicely with important behavioural research by Pascal Haegeli, Ian McCammon, and Laura Adams.

At the beginning of the 2009-2010 season, I wrote a short article on the strategies and tactics of safe winter backcountry travel. When traveling in the backcountry, we all have a set of tactics ( travel technique, snowpack analysis ) that we use to implement our ski trips. This begs the question: what's the strategy? And what procedures are used to uncover and neutralise biases in the strategies we use to reach our objectives? Consider the following model:

objective = strategy + tactics

Now consider that each term in the model is subject to biases that serve as possible sources of error. Have unconscious biases caused you to make an error in your choice of objective? Is Mt. Snoqualmie a suitable objective for current conditions? What about errors in your strategy, such as choosing to ascend Mt. Snoqualmie by Phantom Trees instead of Cave Ridge? Finally, what about errors in your choice of tactics? Are you openly discussing your tactical choices, such as route-finding options, with the other members of your party?

Since dangerous errors are possible at any level ( objective, strategy, or tactic ), it seems important to devise methods of uncovering errors for each level. Products such as the NivoTest, Werner-Munter 3x3 and the Avaluator are designed to help backcountry skiers choose appropriate objectives. However, these products do little to address the relationship between biases and the potential for error at the level of strategy or tactic. While it certainly is true that choosing an objective that is unsuitable for current conditions is likely to result in dangerous strategic and tactical errors, strategic and tactical errors can be just as dangerous even if the choice of objective is reasonable.

For Example: the backside of the Avaluator features obvious clues about snowpack instability, but I wonder if obvious clues about biases such as poor communication and failing to acknowledging uncertainty would be more appropriate? Neither the NivoTest, nor the Werner-Munter 3x3, address these, or other, dangerous biases in any manner whatsoever.

Further research is needed, but since the same biases can affect objectives, strategies, and tactics, I don't think it's terribly difficult to develop sound methods that address biases at all three levels.

Highlights
Some interesting points from the article:

Daniel Kahneman has pointed out, the odds of defeating biases in a group setting rise when discussion of them is widespread. ( His work has been cited by many avalanche researchers. )
Particularly imperiled are senior executives, whose deep experience boosts the odds that they will rely on analogies, from their own experience, that may turn out to be misleading. ( This finding is perfectly aligned with research from Laura Adams. )
Pattern recognition is second nature to all of us—and often quite valuable—so fighting biases associated with it is challenging. The best we can do is to change the angle of vision by encouraging participants to see facts in a different light and to test alternative hypotheses to explain those facts. ( The Avalanche Handbook specifically discusses this as well. )
Most executives rightly feel a need to take action. However, the actions we take are often prompted by excessive optimism about the future and especially about our own ability to influence it. ( This has been discussed by avalanche researchers as well. )
To make matters worse, the culture of many organizations suppresses uncertainty and rewards behavior that ignores it. ( This has been discussed by avalanche researchers as well. )
Superior decision-making processes counteract action-oriented biases by promoting the recognition of uncertainty. ( Managing uncertainty is discussed throughout this blog as a fundamental element of safe winter backcountry travel. )
Stability biases also include loss aversion—the well-documented tendency to feel losses more acutely than equivalent gains—and the sunk-cost fallacy, which can lead companies to hold on to businesses they should divest. ( Or, loss aversion can cause us to continue toward a summit when we should turn around. )
An absence of dissent is a strong warning sign. ( Poor communication. )
To support those new norms, we also need a simple language for recognizing and discussing biases, one that is grounded in the reality of [mountain] life, as opposed to the sometimes-arcane language of academia. ( Avalanche education could use this as well. )

I realise that an article from The McKinsey Journal could seem highly out-of-place in a blog about avalanche safety. Yet, after a second and third read, it's easy to see how dangerous and costly biases become embedded in our decision-making procedures.

This is made all the more difficult by the fact that decision-making errors don't matter when the snowpack is mostly stable, since the chance of triggering an avalanche is relatively low. Over time, as the article points out, these biases become embedded in our procedures and errors arise ... then what happens?

Well, you get to decide.

Free registration is required to read the article.
This paper by Ian McCammon has some interesting insights as well.
Related: New Avalanche Danger Scale
Related: Boulder Mountain Avalanche Accident

My next post discusses the 7 Deadly Sins of Winter Backcountry Travel.

Does Size Matter?

2010-03-02T19:16:00.000-08:00

In a big country dreams stay with you—Big Country

Like people, terrain comes in a bewildering variety of size and shapes and we all have different preferences. Sometimes terrain is obviously dangerous, and other times terrain is obviously safe. At the beginning of the season, I wrote a post about perception of instability. Like instability itself, perception of instability is rarely static. This means that your beliefs about instability change with place and time.

According to The Avalanche Handbook, variations in perception are usually very low when instability is widespread. On the other hand, variations in perception are most frequent, and most dangerous, when instability is not widespread, but not exactly scarce, and when the energy required to release an avalanche is relatively high.

The same rules apply to terrain. Perception of hazard is much better when terrain is obviously dangerous. Perception of hazard is less important when the terrain is actually very safe, since accidents are less likely. Serious errors are most likely when people choose "safe" terrain that sits in the middle of the spectrum. This is a fairly strong claim, but I think it's well-supported by records of skier-triggered avalanches accidents in North America.

Figure 1.1. Scale of terrain evaluation. Terrain is either very safe, very dangerous, or somewhere in between. Where does your secret stash fit on this scale?

Evaluating Terrain
Review the following images and think about where the images belong on the terrain scale. Where are you most likely to travel when snow quality and avalanche hazard are high? Where are you most likely to let your guard down?

Figure 1.2. Mt Currie, British Columbia. COMPLEX terrain featuring exposed alpine features and numerous avalanche paths. Many of these avalanche paths fall more than 1000 metres.

Figure 1.3. Twin Sisters, Washington State. COMPLEX terrain with numerous avalanche paths. Many of these avalanche paths fall more than 1000 metres.

Figure 1.4. Mt. Snoqualmie, Washington State. COMPLEX and CHALLENGING terrain with many safe options. This is exactly the type of middle ground terrain where backcountry skiers are at high risk for perceptual errors. There are many options to reduce exposure, and just as many options for small and medium sized avalanches during poor conditions.

Figure 1.5. Central Cascades, Washington State. CHALLENGING and SIMPLE terrain. As above, there are many options to reduce exposure, and many options for small, but deadly, avalanches.

Why Size Matters
Of all the images, can you take a guess where the most accidents, burials, and fatalities have occurred? The answer is the last image, and it explains why size matters. ( Accessibility is part of the problem as well, but if i can believe what I read on the Internet, many local backcountry skiers believe that the terrain in the last image offers safe options during high avalanche danger. )

Size matters because small avalanches happen much more frequently than large avalanches, especially with respect to skier triggering. Large natural avalanches are relatively rare because enormous slabs can stabilise under their own weight. Large skier-triggered avalanches are rare because the application of dynamic forces from skier influence does not extend much deeper than 1 metre.

However, skiers like to choose terrain in the middle of the spectrum, especially on days when snow quality, and avalanche hazard, are high. Canadian researcher Laura Adams refers to this technique as satisficing: some desirable attributes, such as large, open slopes, are sacrificed while others, such as steepness, are preserved. This technique is definitely valuable, but it has dangerous side effects that contribute to avalanche accidents: choosing terrain in the middle of the spectrum makes it easy to rationalise and let your guard down. The line of thinking is as follows: we sacrificed the big open slopes up in the alpine in favour of steep slopes with trees. The only problem here is that the snowpack and the laws of physics simply don't care about your sacrifices.

The second problem is that most people are killed by avalanches that are, in the big picture, basically tiny. A complete burial requires very little snow, and most slopes that are fun to ski hold enough snow for several bad accidents. These "safe" terrain choices are even more dangerous because most middle ground terrain has at least some tree coverage. A recent study showed that skiers in North America are much more likely to die from traumatic injuries due to trees and rocks, than their counterparts in Europe.

Where I ski in the Washington Cascades and throughout British Columbia, most skiers regard a small slope as ~300 vertical metres, or about 1000 vertical feet. Many popular locations for day trips and yo-yo skiing involve such slopes. At the smallest scale, snowpack information becomes very important: terrain answers the question of is an avalanche possible, and snowpack answers the question of is an avalanche likely. Since it's just as easy to trigger an avalanche on a small, steep slope, it's easy to see why snowpack evaluation can become critically important when small, steep slopes are chosen.

Terrain analysis is one of the best tools for managing uncertainty, but only when slope angles are managed very strictly. Very often, I read trip reports where small, steep slopes are chosen as safe options during times when avalanche hazard is high. This is a fairly poor application of travel technique because small, steep slopes can be just as dangerous as large, steep slopes-especially if you don't seek out specific information about the snowpack.

What are your beliefs about the likelihood of avalanche formation on small, steep slopes? Do you believe small, steep slopes are safer? The record of avalanche accidents in North America provides a clear and resounding answer.

Accidents Involving Small Avalanches

In March of 2008, the author of this blog was buried up to his waist and knees by a soft slab avalanche off a small feature in the Fisher Creek drainage, North Cascades, WA. Skiing alone, I was able to self-rescue in about 40 minutes. It was the second longest 40 minutes of my life.
Close call at Crystal Mountain. More on the avalanche.
A snowshoer killed by a small avalanche at Mount Rainier National Park.
Lou Dawson provides a great account of a small avalanche on WildSnow.
A small avalanche kills a skier in Grand Mesa, Colorado.
Skier partially buried while waiting below a small terrain feature in Colorado.
An avalanche falls 300 vertical feet in unassuming terrain.
What could go wrong in 20 vertical feet?
About half of all fatalities involve avalanches that run less than 90 metres, or about 300 vertical feet.

The Boy Who Drowned

2010-02-22T20:14:00.000-08:00

kominn heim—saeglopur

NOTE: Winter backcountry travel is often a strong focus of avalanche safety. There are many important aspects of avalanche safety at the national and regional levels as well. This post discusses avalanches at the national level, in both the first and third worlds, and also contains links to very personal stories of avalanche involvement. I'll let you decide which is more tragic: national failure or individual failure.

Avalanches As Natural Disasters
The Avalanche Handbook briefly discusses Ian Burton's "richer is better" rule of thumb. This rule applies to natural disasters, and it implies that wealthier societies are better equipped to protect themselves from the wrath of mother nature.

With respect to avalanches, this rule of thumb does not apply in the Western world because many people who choose to expose themselves to avalanches, such as helicopter skiers and backcountry skiers, can only do so because they have sufficient resources.

Avalanches Worldwide
In the third world, poorer is definitely worse. The following articles highlight the difference between avalanches in the first world and avalanches in the third world. It's an eclectic mix of expensive Western engineering, helicopter skiing, and grinding third-world poverty.

Salang Pass Avalanches, Telegraph UK, Contains Graphic Imagery!
Salang Pass Avalanches, United Nations, Contains Graphic Imagery!
Salang Pass Avalanches, United Nations, Contains Graphic Imagery!
Avalanche Control, by United Nations FAO
Review of The Avalanche Enigma, Sports Illustrated 1966
Tragedy On Bay Street, Sports Illustrated 1991
Snow Blind, Sports Illustrated 1991
Avalanche!, Sports Illustrated 1982
A Deadly Avalanche, Sports Illustrated 2003
A Thin, White Line, Ted Kerasote 2003
History of the SLF, SLF Switzerland
How Are Avalanche Bulletins Produced?, SLF Switzerland
Planning Avalanche Defence Works For The Trans-Canada Highway At Rogers Pass, NRCAN
The Snow War, ParksCanada
The Swiss Guides, ParksCanada

Are you spending your hard-earned money to access avalanche terrain? What's your desired rate of return?

Washington Terrain Ratings

2010-02-19T16:38:00.000-08:00

It's the little things that kill—Bush

DISCLAIMER
TRAVELING IN AVALANCHE TERRAIN MAY RESULT IN SERIOUS INJURY OR DEATH. THESE TERRAIN RATINGS DO NOT CONSIDER CRITICAL FACTORS RELATED TO AVALANCHE FORMATION SUCH AS CURRENT WEATHER OR THE STRUCTURE OR MECHANICAL STABILITY OF THE SNOWPACK. NONE OF THE TERRAIN RATED IN THIS DOCUMENT IS COMPLETELY SAFE FROM AVALANCHES. THESE TERRAIN RATINGS DO NOT CONTAIN ANY INFORMATION ON CURRENT INSTABILITY NOR ANY FORECAST OF FUTURE INSTABILITY. YOU BEAR FULL RESPONSIBILITY FOR THE CONSEQUENCES THAT MAY ARISE FROM YOUR CHOICES.

Terrain Ratings
Most people are familiar with the idea of terrain ratings, but if you are not familiar with the ATES technical model, review the following video:

Introduction
This document contains terrain ratings for ski trips in Washington State. These terrain ratings provide an overall picture of the avalanche exposure for the terrain listed. The author's interpretation of ATES parameters are as follows:

The ATES rating system considers avalanche exposure. Other hazards exist.
The amount of exposure increases by at least 1 order of magnitude for each rating level.
Exposure to avalanche terrain does not increase in a linear manner.
Exposure for a simple tour might be viewed as a value of 4.
Exposure for a challenging tour is 16.
Exposure for a complex tour is 64.
In addition many tours have elements of each classification but these ratings are constructed with the entire tour, including the return, in mind.
Tours rated challenging are not conservative choices when the danger rating is considerable or higher.
Combine these ratings with the current avalanche danger and your personal risk acceptance level.

Simple
Exposure to low angle or primarily forested terrain. Some forest openings may involve the runout zones of infrequent avalanches. Many options to reduce or eliminate exposure. No glacier travel. Choose these trips when avalanche danger is Considerable or higher.

Aiken Lava Bed
Alpental To Source Lake
Amabilis Mountain
Artist's Point
Clara Lake
Hidden Valley Snoqualmie Pass
Hyak Nordic Trails
Diamond Head Road Ski
Diamond Head Trees
Earl Peak Approach via Bean Creek ( Before Climbing To Earl Pass )
Heather Ridge To Skyline Lake
Icicle Ridge
Marble Mountain
Merritt Lake
Mt. Angeles
Narada Falls To Reflection Lakes ( Avoiding the obvious avalanche slope near the parking lot. )
Narada Falls To Paradise
Olympic National Park Lodge Run
Olympic National Park Toilet Bowl
Olympic National Park Waterhole Trail
Olympic National Park Obstruction Point Ridgeline Tour
Olympic Hot Springs
Paradise to Glacier Vista
Silver Basin Flats ( No travel on steep, open slopes around the basin. )
Stetattle Ridge

Challenging
Exposure to well defined avalanche paths, starting zones or terrain traps; options exist to reduce or eliminate exposure with careful route-finding. Glacier travel is straightforward but crevasse hazards may exist. Choose these trips when avalanche danger is moderate.

Alpental To Ridge Above Snow Lake
Cement Basin
Castle / Pinnacle Saddle
Crystal Lake Basin Forested Slopes
Diamond Head Chutes
Eagle Mountain
Earl Peak Approach via Bean Creek, Including Uphill To Earl Pass
Goat Rocks To Treeline
Governor's Ridge
Heather Ridge Backside
Heather Ridge Moonlight Bowl
Hurricane Ridge
Jim Hill Mountain
Jove Peak Approach
Jove Peak South Face Lower Slopes
Kendall Ridge
Lake Stuart
Lichtenburg Mountain North Side
Marmot Pass, To Treeline
Mazama Back Bowls
Mazama Ridge Ski Slopes
Mission Peak
Mt. Catherine
Mt. Margaret
Mt. Roosevelt
Mt. Tamanos
Naches Peak
Narada Falls to Reflection Lakes ( travel up or down the obvious avalanche slope ).
Norse Peak
Paradise To Cowlitz Rocks
Paradise to Panorama Point or McClure Rock
Paradise To Stevens Canyon Via Road
Peak 7828 approach only.
Phantom Trees ( Up to 600 vertical feet / 200 vertical metres below summit. )
Pickhandle Basin
Skyline Ridge
Silver Basin Lower Slopes ( up to the party knoll )
Tunnel Creek ( South side of Cowboy Mountain, Stevens Pass ).
Wedge Mountain, Travel Confined To Ridges, Forested Slopes
Yakima Peak
Yodelin Trees

Complex
Exposure to multiple overlapping avalanche paths or large expanses of steep, open terrain; multiple avalanche starting zones and terrain traps below; minimal options to reduce exposure. Complicated glacier travel with extensive crevasse bands or icefalls. Choose these trips when avalanche danger is moderate or low.

Alaska Mountain
Bacon Peak
Big Slide Peak Summit & North Face
Burroughs Mountain
Butter Creek Drainage
Boston Basin
Camp Muir to Nisqually Bridge
Cannon Mountain Northwest Face via Avalanche Path and Central Colouir.
Cashmere Mountain Summit
Cashmere Mountain Traverse
Chair Peak Circumnavigation
Chair Peak South Basin
Chickamin Peak
Clark Mountain
Colchuck Peak
Colfax Peak
Cowlitz Chimneys
Crystal Lake Basin Open Slopes
Crystal Mountain To Chinook Pass
Cutthroat Pass
Cutthroat Ridge Descents
Dome Peak
Dragontail Peak
Earl Peak Southwest Face
Earl Peak Southeast Face
Earl Peak North Bowls
Eightmile Mountain
Eldorado Peak
Forbidden Peak
Fuhrer Finger
Glacier Peak
Goat Island Mountain
Goat Pass ( Mt. Stuart Area )
Goat Rocks Alpine
Grindstone Mountain
Heliotrope Ridge
Hidden Lakes Peak
Horseshoe Lake
Jack Ridge
Jove Peak South Face From Summit
Lichtenburg Mountain South Side
Lichtenburg Mountain West Side
Lichtenburg Mountain Summit
Lundin Peak
Marmot Pass, To Saddle
Mt. Adams
Mt. Baker Summit
Mt. Buckner
Mt. Howard Summit
Mt. Olympus
Mt. Mastiff Summit
Mt. Maude
Mt. Rainier Carbon Glacier
Mt. Rainier Sunset Amphitheatre
Mt. Rainier Liberty Ridge
Mt. Rainier Summit
Mt. Rainier Glacier Basin
Mt. Rainier Steamboat Prow
Mt. Saint Helens
Mt. Snoqualmie To Summit
Mt. Ross to Davis Peak Traverse
Mt. Shuksan
Mt. Stuart
Mt. Stuart Sherpa Glacier
Mt. Terror
Mt. Triumph
Olympic National Park Klahane Ridge
Paradise to Camp Muir
Peak 7828 To Summit
Ptarmigan Traverse
Pyramid Peak
Red Mountain
Reflection Lakes To Castle Peak
Reflection Lakes To Pinnacle Peak
Rock-Howard-Mastiff Mountain Traverse
Rock Mountain Summit
Ruby Mountain
Sahale Arm
Sarvant Glaciers
Silver Basin Upper Slopes ( to ridgeline or summit of Silver King )
Silver Star Mountain
Sinister Peak
Skidgravel Peak
Slot Couloir
Sylvester Lake
Tatoosh Range Traverse
Table Mountain
Three Fingers Mountain
Tower Mountain Northeast Couloir
Unicorn Peak
Union Creek
Van Trump Park
Vesper Peak
Wedge Mountain, ( Any Travel On East Face )
Whitehorse Mountain

Credits

These ratings use the ATES technical model, a product of ParksCanada and the Canadian Avalanche Centre.
Ratings were constructed with the help and guidance of participants on http://www.turns-all-year.com/.