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Special message in the March 3rd CAC Avalanche Bulletin

4 Mar 2010

Link to CAC Bulletins: www.avalanche.ca/cac/bulletins/regions

Special Message

Yikes! We continue to get reports of wild avalanches showing huge propagations. Link to photos. The danger ratings, while technically correct, don't fully convey the magnitude of the problem. I recommend avoiding avalanche terrain unless you have high level training, lots of experience, and/or extensive local knowledge about the layers in the upper snowpack and recent avalanche activity.

Avalanche Activity

Avalanches big enough to kill a person are occurring frequently and occasionally we are hearing of avalanches large enough to destroy a train engine. Slides are being triggered by light loads such as skiers or even spontaneously with warming temperatures. Most of these avalanches are occurring on north, east and west aspects at treeline and in the alpine. As these conditions progress I expect the frequency of avalanches may drop slightly as they get harder to trigger, but they will almost certainly stay big and destructive for a long time to come.

Travel Advisory

Terrain to Avoid: I would stay off anything over 20 degrees on shady aspects. Be especially wary of loaded pillows of snow with slight convexities or undulating rolls. Be off the south aspects once the sun has started to melt and soften the surface.
Techniques to Manage Risk: Get an early start to the day to avoid the increasing hazard with rising temperatures. Sticking to the due south facing slopes early in the day may reduce your exposure to the surface hoar weaknesses. Even if the skiing there is terrible it’s a better option to make sure you come home at the end of the day.

Snowpack

OK. So the quote of the week is “the snowpack doesn’t really get any worse”. There are still 3 significantly weak surface hoar layers in the upper metre. The weakest one is down 30-60cm, where tests still show easy results and skiers are easily triggering slab avalanches on this layer. The wind created a slab on the surface on much of the alpine and treeline snow. The sun has created a crust on south aspects up to ridge-crest, which softens in to moist snow by the afternoon. One advantage of the crust is, while it’s still cold and frozen, it will hold the upper snowpack together so it is much less likely to trigger an avalanche on the South aspects until the crust melts later in the day