Avalanche Forecast
Issued: Dec 1st, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
ahanna,
Avalanche Canada
Wind slabs at upper elevations will be driving avalanche danger on Thursday. Be alert as you transition into wind-affected elevations and stay off recently wind loaded slopes until they've had a chance to stabilize.
Summary
Confidence
Weather Forecast
Wednesday night: 5-10 cm new snow. Strong southwest wind. Alpine temperature around -10 C. Freezing level dropping to valley bottom.
Thursday: 5-10 cm new snow. Strong southwest wind. Alpine temperature around -12 C.
Friday: 5-15 cm new snow. Strong southwest wind. Alpine temperature around -10 C.
Saturday: 5-10 cm new snow. Moderate southwest wind. Alpine temperature around -12 C.
Avalanche Summary
On Wednesday morning, a few small naturals were observed and explosive and machine control work produced size 1-2 storm slab avalanches.
On Tuesday morning several size 2 storm slabs were reported to have run naturally during the storm.
Over the weekend, several large natural storm slabs (size 2-3) were reported in the alpine as well as some small loose wet avalanches near the rain line.
Snowpack Summary
30-60 cm of recent heavy storm snow has been stripped from ridgetops and exposed terrain and loaded into lee (north to east-facing) terrain features and cross-loaded slopes by strong to extreme wind at upper elevations. At elevations below treeline where the snow hasn't been washed away altogether, expect a surface crust to form in the cool temperatures.
A crust that formed as high as 1600 m during a previous warm November storm is now 50-100 cm deep. Wind slabs have shown good propagation where they sit directly over this slick sliding surface.
In the Northern part of the region (Bear Pass) two weak layers of surface hoar from early to mid November have been reported in sheltered areas at treeline.
Treeline snowpack depths are estimated to be around 2-3 m and a prominent crust can be found near the base of the snowpack.
Terrain and Travel
- Be alert to conditions that change with elevation and wind exposure.
- Avoid lee and cross-loaded slopes at and above treeline.
- Wind slabs may be poorly bonded to the underlying crust.
- A crust on the surface will help bind the snow together, but may make for tough travel conditions.
Problems
Wind Slabs
Strong to extreme winds have blown recent storm snow into thick wind slabs in lee terrain features and cross-loaded slopes at upper elevations. Wind slabs may be especially reactive where they sit on top of a slick crust.
Cornices have reportedly formed along ridgelines. Cornice failures can trigger avalanches on the slope below.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 2nd, 2021 4:00PM
