Avalanche Forecast

Issued: Dec 16th, 2012 8:37AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs and Deep Persistent Slabs.

Avalanche Canada istorm, Avalanche Canada

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Synopsis: On Monday & Tuesday the region will see a cool unstable onshore flow with light SW winds, light snowfall with no significant accumulation, and freezing level near valley bottom. The next system is not arriving until sometime Wednesday when a Gulf of Alaska Low starts sliding south off the coast.

Avalanche Summary

In areas with deeper storm snow accumulations (for example near Stewart) natural avalanches to size 2.5 were reported; otherwise no new naturals reported but visibility was limited.

Snowpack Summary

Storm snow accumulations in the north and near the coast (for example the mountains near Stewart) are as high as 65 cm; away from the coast there was much less. For example near Shames it was closer to 20 cm of storm snow but the total snowpack depth only added 5 cm due to settling. The upper snowpack should be mostly settling powder depending on elevation. I expect wind slabs or wind affected snow in higher elevation exposed areas. Deeper in the snowpack professionals continue to monitor a crust down near the ground. It seems this problem is confined to  alpine areas and likely needs a large trigger and / or a shallow snow pack feature to trigger.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm snow instabilities are possible on steeper slopes where new snow accumulations are greater than 30 cm. New windslabs are likely behind ridges, ribs, or similar terrain breaks.
Assess start zones carefully and use safe travel techniques.>Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deeply buried weaknesses exist. Dropping cornices or smalller surface slides could step down.
Avoid shallow snowpack areas where triggering is more likely.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 7

Valid until: Dec 17th, 2012 2:00PM