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: Mostly cloudy, clearing Friday morning. 2-8 cm of snow expected. Light to moderate southwest winds, trending to strong at high elevations in the far south end of the region. Freezing level at valley bottom.
Friday: A mix of sun and cloud. 0-2 cm of snow expected. Up to 5 cm in the Coquihalla area. Light north winds, trending to southwest at higher elevations. Temperature @ 1500m dropping to around -13 C.
Saturday: Mostly cloudy. 2-5 cm of snow expected. Light northeast winds trending to strong southwest at higher elevations. Temperature @ 1500 m dropping to around -17 C.
Sunday: A mix of sun and cloud. 0-2 cm of snow expected. Light to moderate north winds, trending to southeast at higher elevations. Temperature @ 1500 m around -25 C.
Avalanche Summary
No new avalanches were reported on Thursday, but not many professional operations or recreators have reported recently. Remember that a lack of reports does not necessarily mean a lack of avalanche activity.
In neighbouring regions with similar storm totals, the storm slabs were reported to be reactive, with avalanche control producing many size 2 avalanches. Also a couple of smaller, skier triggered avalanches were reported in steep, unsupported terrain.
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
30-60 cm of storm snow fell Tuesday night through Thursday, with moderate to strong south through southwest winds. Expect the new snow to be deeper and slabbier on leeward slopes.
This 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 Mountain Information Network (MIN) post from Tuesday paints a great picture of the conditions around the Wendy Thompson hut before the bulk of the storm.
A concerning layer of facets (sugary snow) can be found over a widespread crust that formed in early December (down 70-150 cm). This layer has been 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 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.
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Problems
Storm Slabs
Moderate to strong south through southwest 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
A layer of weak facets (sugary snow) can be found down 70-150 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
