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 30 cm, strong southwesterly winds, low treeline temperatures near -2 C with freezing level going down 600 m.
Thursday: Mainly cloudy with isolated flurries, 1-2 cm, moderate westerly winds, high treeline temperatures near -5 C with freezing level at 500 m.
Friday: Periods of snow, 10-15 cm, light to moderate southwesterly winds, high treeline temperatures near -5 C with freezing level at 300 m.
Saturday: Flurries, 5 cm, ligth to moderate southwesterly winds, high treeline temperatures near -8 C with freezing level at valley bottom.
Avalanche Summary
Although avalanche activity has momentarily tappered off on Monday and Tuesday, we are expecting natural avalanche activity to continue on Thursday with additional storm snow and strong southwesterly. 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 60 to 75 cm to the 30 to 40 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.
In the north of the region, a concerning layer of facets (sugary snow) can be found down 100-200cm over a crust that formed in early December. This layer seems particularly reactive in thinner snowpack areas near ridge tops, where the facets are more developed and where the crust layers are more accessible to the weight of a person or machine. Large size 2 and 3 avalanches on this persistent slab problem have been reported over the past few days in the neighbouring Sea-to-Sky region. 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
In the north of the region, 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
