Winter is here…food for thought

It’s November again, which means in many parts of the country, winter has begun.

There are snow men in yards, sleds with giggling kids, and in my neck of the woods, parking lots packed with powder starved skiers and riders.

During the last couple years, there were a number of high profile accidents and the ski and snowboard communities lost close friends and family.  As I reflect on our community’s losses, I have begun to ponder tools that can help the rest of us stay safer.

Looking back on several of the accidents that occurred during the last couple winters, I can only think that the avalanche problem was mis-identified by the parties involved.

What do I mean by this?

Several years ago, the Utah Avalanche Center introduced seven avalanche problems on their forecast page (though the original avalanche characterization goes back to Roger Atkins in 2006).

Avalanche Problems

Each of these problems has a unique habitat (although many overlap), a different way of forming and developing, and different forecasting and management challenges.  If we can identify the problem, or problems, we can begin to forecast where these problems might exist, the size of the problems, the predictability of these problems, and the manageability of the problems.

Loose snow avalanches are found on, or near, the surface.  Loose snow tends to form small avalanches that are significant primarily in extreme terrain.  This problem tends to be predictable and easily managed.

Storm snow is also found on or near the surface.  It can form small to large avalanches.  This problem is easily to moderately predictable and an easy to moderate management problem, depending on the size of the storm slab, how rapidly it forms, and how long it has been since it was deposited.

Wind slab is a cohesive layer found when wind deposits snow on the lee side of terrain features.  It is found in the upper part of the snowpack where the wind blows – typically on leeward aspects, at or below ridgelines, in gullies and other terrain features.  Wind slabs are easy to predict and can be easy to moderately difficult to manage.  Typically the harder the wind blows, the stiffer the wind slab, the more difficult the management problem.  Wind slabs are often triggered where the slab thins out towards its edges.

Persistent Slabs are found in the upper to mid pack.  Persistent slabs rest on persistent weak layers – facets, depth hoar, surface hoar, or mixed forms. Unstable conditions may exist for days to weeks when dealing with persistent weak layers and persistent slabs.  The older the persistent slab, the more difficult it may be to trigger, but the larger it may be when it releases. Persistent slabs are difficult to predict.  They are also difficult to manage.

Deep Slabs are large destructive slabs that slide on a persistent weak layer.  Deep slabs persist for weeks or months.  These slabs are very difficult to forecast and very difficult to manage.  They, like persistent slabs, can release when the third, fourth or sixteenth person crosses a slope.  The main differentiator between persistent slabs and deep slabs is the size of avalanche they create.  If an avalanche that runs on a persistent weak layer is capable of burying a car,  it more likely to move into the deep slab category.

Wet Slab avalanches are caused by a cohesive slab of snow losing its bond to an underlying weaker layer or interface after becoming damp, moist, or saturated with water. Extended periods of above freezing temperatures, strong solar radiation, and rain can form wet slabs.  They range from being easy to difficult to forecast and just as easy to difficult to manage. It is important to recognize the weather patterns that form wet slabs.  The trickiest time for wet slab forecasting is in the spring when the snowpack is making a transition from cold and dry snowpack to a warm (0°C) wet snowpack.

Cornices are easy to identify.  Cornices are formed as a result of wind, and form on the leeward side of a ridge or other terrain feature.  Cornices are difficult to manage.  The best strategy is to give cornices a wide berth…often wider than you think necessary.

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Avalanche forecasters build their forecasts based on the avalanche problem, the distribution of this problem, and the likelihood of triggering this problem.  While developing an avalanche hazard forecast can be a challenge for even the most experienced backcountry enthusiast, identifying the avalanche problem is an attainable goal for all of us.

The bottom line is that safe backcounty travel begins with good pre-trip planning. Understanding the avalanche problem, or problems, and where these problems might be present before heading out on a tour is an important piece of avalanche safety.

Other important pieces of the pre-trip planning puzzle are checking your local forecast, choosing terrain that is appropriate for the current avalanche forecast and the identified avalanche problems; and choosing partners that are prepared, well-trained, and have a similar risk tolerance to you.  A generalization that seems to hold true for most avalanche accidents was that skipping steps in the planning of the tour significantly contributed to the accident.  Five or ten minutes more on the front end might have prevented some of these accidents.

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Ski and ride hard, have fun with your friends, but remember that traveling in avalanche terrain is not too dissimilar to climbing.  Proper preparation, well-maintained gear, trusted partners, and thoughtful route choices based on conditions are all essential.

To learn more about the avalanche problems, take an avalanche class.  You can also check out these great online resources:

http://www.avalanche.ca/cac/training/online-course/avalanche-formation/Avalanche-problems

http://utahavalanchecenter.org/avalanche-problems-tutorial

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