Avalanche Forecast
Issued: Dec 22nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
dboucher,
Avalanche Canada
Recent major storm has develop significant storm slabs that remain reactive with the potential to step-down and trigger deeper buried weak layer. Avoid avalanche terrain and wait for conditions to improve.
Summary
Confidence
Weather Forecast
Snow continues as moisture will persist in the extreme south of the province, favouring additional snowfall for the South Coast mountains.
Wednesday night: Snow, heavy at times, 25 to 40 cm, strong southerly winds, low treeline temperatures near -7 C with freezing level going down to valley bottom.
Thursday: Mainly cloudy with isolated flurries, 2-4 cm, light to moderate westerly winds, high treeline temperatures near -10 C with freezing level at valley bottom.
Friday: Flurries, 5 cm, light to moderate easterly winds, high treeline temperatures near -10 C with freezing level at valley bottom.
Saturday: Flurries, 5 to 10 cm, light to moderate easterly winds, high treeline temperatures near -12 C with freezing leval at valley bottom.
Avalanche Summary
A few wind slab avalanches triggered by skiers have been reported Tuesday in Pemberton area. With additional storm snow and strong southwesterly winds, we are expecting natural avalanche activity to continue on Thursday. Storm slabs avalanches have the potential to step-down to recently reactive buried weak layers, with the potential to produce very large, destructive avalanches. Cornices may also reach their breaking point, triggering persistent slab avalanches on slopes below.
Snowpack Summary
The ongoing storm has the potential to add 70 to 100 cm to the 30 to 50 cm layer of settling snow from last weekend's storm. All this new snow sits on a variety of snow surfaces, hard wind-scoured surfaces, preserved powder, and possible surface hoar in sheltered areas. Strong southerly winds will continue to redistribute the storm snow into dense wind slabs on leeward terrain features.
A culprit weak layer of facets (sugary snow) can be found over a widespread crust that formed in early December (down 100-200 cm). This layer seems particularly reactive at lower alpine and treeline elevations, between 1500-2100 m. Large size 2 and 3 avalanches on this persistent slab problem have been reported over the past few days. This problem is particularly hard to predict and tricky to manage. Given the rapid load from the storm and wind, this persistent slab problem requires to scale back and wait for conditions to improve. Get more details and photos in our forecaster blog.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Give the new snow time to settle and stabilize before pushing into bigger terrain.
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
Problems
Storm Slabs
Storm snow and strong southwesterly winds have developed large storm slabs we expect to continue to be reactive troughout the day.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 100-200 cm near a crust that formed in early December. Storm slabs in motion may step down to this layer and trigger large destructive avalanches. Also, it is more likely to human trigger this persistent slab in thick to thin areas at tree line elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 23rd, 2021 4:00PM
