Avalanche Forecast
Issued: Dec 20th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Northwest winds may form wind slabs in areas that are usually more windward, which could catch riders off guard.
Seek out sheltered terrain where you can avoid these wind slabs and find great riding.
Summary
Confidence
Weather Forecast
Monday Overnight: Partially cloudy with the chance of light flurries, trace accumulation. Light to moderate west winds at ridgetop. Alpine temperatures near -15 C.
Tuesday: A mix of sun and cloud, increasing cloud cover in the afternoon. Moderate to strong west winds at ridgetop, increasing in the afternoon. Snowfall beginning overnight with 5-15 cm of accumulation. Temperatures rising to -7 C in the alpine by morning.
Wednesday: A stormy day. Moderate to strong southwest winds will accompany steady snowfall. There is the potential for locally heavy accumulations of upwards of 30 cm throughout the day. Freezing level rising to 1000m in the afternoon. Continued snowfall overnight with another 10-40 cm of accumulation.
Thursday: Continued snowfall, another 10-30cm of accumulation heaviest in the morning. Moderate to strong southwest winds easing into the afternoon to light to moderate. Freezing levels dropping in the evening to valley bottom.
Avalanche Summary
On Monday, operators ski cut storm slab and loose dry avalanches up to size 1.
On Sunday, operators reported a natural avalanche cycle from overnight, with avalanches up to size 3 running almost full path. Explosive control work produced size 1-2.5 storm slabs in the alpine and treeline.
On Sunday, one notable ski cutting result produced a size 1.5 persistent slab avalanche at treeline on the early December crust.
Snowpack Summary
An intense storm came through the region on Saturday, bringing 40-70 cm of new snow. Overnight, northwest winds will have redistributed this new snow into wind slabs in the alpine and treeline. The northerly component to winds will potentially creating loading in more atypical areas at higher elevations. Throughout the day, winds will shift southwest and continue to transport available snow into fresh wind slabs.
Below this new snow, 50-100 cm of more consolidated snow sits over a substantial crust that formed in early December. This crust is up to 20 cm thick and is present across all aspects below 2400m. A layer of weak facets (sugary snow) can found above this crust. This problem is particularly hard to predict and tricky to manage. For this reason wide, conservative terrain margins and disciplined backcountry travel techniques will be very important. Get more details and photos in our forecaster blog.
The lower snowpack consists of a variety of early season crusts and mainly moist snow. Snowpack depths range from 100-200 cm at treeline elevations and taper quickly below 1800 m.
Terrain and Travel
- Be careful as you transition into wind affected terrain.
- Be aware of highly variable recent wind loading patterns.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
Saturday's intense storm brought 50-70 cm of new snow. Overnight northwest winds will continue to redistribute this new snow into wind slabs in the alpine and treeline. The northerly component to winds may create loading in areas that are not commonly loaded. Continued southwest wind throughout the day today will transport available snow into fresh, reactive wind slabs in the alpine and treeline.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 100-150 cm over a crust that formed in early December. There have reports of natural and human triggered avalanches on this layer during the last storm in areas where the overlying slab is shallower. For this reason, it is important to avoid thick to thin areas, shallow rocky start zones, and areas where a meter or less of snow overlies the crust.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2021 4:00PM
