Avalanche Forecast
Issued: Dec 15th, 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.
astclair,
Avalanche Canada
Watch for changing conditions in wind-exposed areas. If winds pick up, fresh reactive wind slabs are likely to form. Avoid slopes where slab properties exist above a persistent weak layer.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Wednesday night: Scattered clouds, no new snow expected, light to moderate southwest winds, alpine temperatures near -13 C.
Thursday: Mainly cloudy, scattered flurries with up to 5 cm of snow beginning in the afternoon, light to moderate southwest winds trending westerly with strong gusts at higher elevations, alpine high temperatures near -11 C.
Friday: Mostly clear, up to 5 cm of snow expected overnight, light west winds increasing to moderate at higher elevations, alpine high temperatures near -11 C.
Saturday: Partly cloudy, up to 5 cm of new snow, southwest winds increasing to moderate with strong to extreme westerly winds in the alpine, alpine high temperatures near -5 C.
Avalanche Summary
It may be possible to trigger slab avalanches in wind-drifted areas at upper elevations or where a slab overlies weak snow on a crust.Â
On Wednesday, operators reported two large (size 2) explosive-triggered avalanches that broke 30-4 cm deep in the storm snow. There was also a report of an explosive-triggered dry loose avalanche in complex terrain.
On Tuesday, avalanche control with explosives produced numerous size 1-1.5 avalanches in the recent storm snow.
Snowpack Summary
20-30 cm of snow has accumulated since Monday with very little wind. This fresh snow likely remains unconsolidated, except where the wind is drifting it into denser slabs at upper elevations.Â
Below this layer, consolidated snow from the previous weekend storm sits over a substantial crust that formed in early December. This crust is likely 20 cm thick (or more) and is present across aspects below 2400m. A thin layer of weak facets (sugary snow) can found above this crust . This persistent weak layer has demonstrated recent propagation potential in snowpack tests. Check out our field team's MIN report from the Barnes Lake area for more details.
The lower snowpack consists of a mix of various early season crusts and mainly moist snow. Snowpack depths range from 55-170 cm at treeline elevations and taper quickly below 1800 m.
Terrain and Travel
- Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
- Make observations and assess conditions continually as you travel.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Uncertainty is best managed through conservative terrain choices at this time.
Problems
Wind Slabs
It may be possible to trigger avalanches in the recent snow where it is getting drifted into cohesive slabs at upper elevations.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A layer of weak facets (sugary snow) can be found down 50-90 cm over a crust that formed in early December. This layer has demonstrated reactivity in snowpack tests and warrants conservative terrain selection.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 16th, 2021 4:00PM
