Avalanche Forecast
Issued: Dec 23rd, 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.
bchristie,
Avalanche Canada
Choose simple, well supported terrain without convexities. It's a bit too soon to jump into bigger, steeper, open terrain. Slabs formed during the storm can still avalanche under the weight of a rider.
Summary
Confidence
Weather Forecast
Thursday Night: Overcast. 2 cm of snow expected. Moderate southwest winds, with strong southeast early friday morning. Freezing level falling to 400 m.
Friday: Overcast. 15 cm of snow expected. Moderate southeast to south winds in the morning, tapering to light in the afternoon. Freezing level rising to 500 m.
Saturday: Overcast. 10 cm of snow expected. Moderate southwest winds trending to strong south at higher elevations. Freezing level falls to sea level.
Sunday: Mostly cloudy with possible sun in the afternoon. 0-2 cm of snow expected. Light to moderate southeast winds. Temperature @ 1500 m dropping to around -15 C.
Avalanche Summary
No new avalanches were reported on Thursday prior to publishing, but the storm snow was reported to be reactive to explosives and rider triggers in the Sea to Sky region.
On Wednesday in the North Shore Mountains, a few natural and skier triggered wet loose avalanches were reported to size 1, running on a crust from December 21.
Storm slab avalanches have the potential to step-down to recently reactive buried weak layers, with the potential to produce very large, destructive avalanches.
Snowpack Summary
20-40 cm of storm snow fell Tuesday and Wednesday with generally strong southwest winds. Expect the new snow to be deeper and slabbier on leeward slopes.
This Mountain Information Network (MIN) post from near Mt. Seymour shows that snowfall amounts could be variable across the region.
The new snow sits on a variety of snow surfaces: variable wind slabs and hard wind-scoured surfaces in terrain exposed to the wind, and preserved powder and possible surface hoar in sheltered areas.
This MIN post from east of Squamish paints a great picture of the below treeline snowpack before the bulk of the storm.
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 has been recently 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 recently in the neighbouring Sea-to-Sky region. This problem is particularly hard to predict and tricky to manage. Get more details and photos in our forecaster blog.
Terrain and Travel
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Give the new snow time to settle and stabilize before pushing into bigger terrain.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
Problems
Storm Slabs
Storm snow and strong southwesterly winds have developed large storm slabs that may still be reactive to riders.
These slabs may become less reactive as they settle after the storm, and as temperatures get colder, but give them some time to bond to the rest of the snowpack.
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 thin areas at tree line elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
