Avalanche Forecast

Issued: Dec 5th, 2020 4:00PM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada astclair, Avalanche Canada

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Low hazard doesn't mean no hazard. Keep in mind that stiff wind slabs may linger in isolated or extreme features.

Summary

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Saturday night: Clear skies, moderate southwest winds with stronger westerly winds over the divide, no precipitation, freezing level drops to valley bottom. 

Sunday: Mostly clear, light to moderate southwest winds with stronger westerly winds over the divide, no precipitation, alpine high temperatures reaching -3 C, freezing level rising to 1300 m.

Monday: Mix of sun and cloud, moderate southwest winds with strong to extreme westerly winds across the divide, no precipitation, alpine high temperatures reaching -2 C, freezing level rising to 1400 m. 

Tuesday: Increasing cloud, moderate southwest winds with stronger westerly winds over the divide, isolated flurries with trace accumulations, alpine high temperatures reaching -1 C, freezing level rising to 1700 m. 

Avalanche Summary

At the beginning of last week's strong temperature inversion, predictable small (up to size 1.5) loose wet avalanches were observed on steep solar slopes and in extreme rocky terrain.

There have been no reports of large avalanches in the past week. The most recent wind slab avalanche activity was reported at the end of November. 

Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! 

Snowpack Summary

After several days of clear skies and warm air in the alpine, temperatures are returning to their seasonal normal, and melt-freeze crusts have been left behind on solar aspects. Strong west and southwest winds previously scoured upwind slopes and ridges and deposited snow into stiff wind slabs on lee or cross-loaded features. These old wind slabs may sit above a widespread rain crust from early November, which can be found up to 2500m and buried down 30-100cm. Weak snow may be developing around this crust. However, given the stagnant weather pattern and decreasing trend in instability, this problematic snowpack structure is not currently listed as a problem. We can expect to see it transition to our problems page with the next snowfall. It will be a feature to monitor as the season progresses.

The snowpack is thin and variable in wind-scoured areas, and it tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are nearing 100 cm and beginning to exceed the threshold for avalanches. 

Terrain and Travel

  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

Problems

Wind Slabs

An icon showing Wind Slabs

Previously strong winds deposited hard wind slabs on lee and cross-loaded features at upper elevations. You may encounter a remaining stubborn wind slab in isolated areas in the alpine and in "alpine-like" features near treeline, particularly where these slabs sit on top of a crust/facet layer from early November.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

1 - 1.5

Valid until: Dec 6th, 2020 4:00PM

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