Avalanche Forecast
Issued: Dec 24th, 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 your terrain carefully, and avoid thin, rocky start zones. Storm slabs will be most reactive at ridge crests and steep rolls, and an unpredictable persistent slab problem is still lurking.
Summary
Confidence
Weather Forecast
Friday Night: Partly cloudy. 0-5 cm of snow expected. Light north winds trending to moderate southwest at higher elevations. Temperature @ 1500 m dropping to around -15 C.
Saturday: Mostly cloudy, possible periods of sun in the afternoon. 5-10 cm of snow expected. Light north winds trending to strong south 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 east at higher elevations. Temperature @ 1500 m around -25 C.
Monday: Sunny in the morning, partly cloudy by the afternoon. No new snow expected. Light northwest winds, trending to strong at higher elevations. Low temperature @ 1500 m around -25 C.
Avalanche Summary
On Friday, a skier triggered size 2.5 persistent slab avalanche was reported in the backcountry near Blackcomb. It was around 110 cm deep, in a northwest facing feature around 2100 m. Last week's forecaster blog is still relevant.
No new avalanches were reported in this region on Thursday or Friday.
In neighbouring regions with similar storm totals, the storm slabs were reported to be reactive, with avalanche control producing many size 2 avalanches.
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
10-20 cm of new, low density snow overlies 30-60 cm of snow that fell Tuesday night through Thursday, with moderate to strong south through southwest winds. Expect the wind transported snow to be deeper and more reactive on leeward slopes. Watch for local variation in wind directions. For example, this Mountain Information Network (MIN) Post describes windslabs at and above treeline from northwest winds in the Cayoosh Pass area.
Also from the Cayoosh area, here is another MIN report looking deeper into the snowpack.
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
- Start with simple terrain and gather information before thinking about more committing features.
- 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.
Problems
Storm Slabs
Continued snow and moderate to strong south through southwest winds are building storm slabs that may 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.
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 25th, 2021 4:00PM
