Avalanche Forecast

Issued: Dec 2nd, 2020 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs.

Avalanche Canada astclair, Avalanche Canada

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Make note of the snow surface condition ahead of the next snowfall. A weak layer near the bottom of the snowpack remains possible to trigger.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Wednesday night: Increasing cloud, moderate southwest wind, freezing level dropping to 500 m.

Thursday: Mostly cloudy, a trace of new snow, moderate southwest wind, freezing level between 500 and 700 m.

Friday: Cloudy, 5-10 cm of snow, moderate southwest wind, freezing level rising to 1200 m

Saturday: Cloudy, 5-15 cm of snow, moderate to strong southwest wind, freezing level rising to 1500 m. 

Avalanche Summary

Observers reported natural avalanche activity on Tuesday. A large (size 2.5) wind slab near Hudson Bay Mountain released naturally and may have stepped down to a deeper crust layer. Further north in the region, a cornice fall triggered a large (size 2.5) deep persistent slab avalanche that ran on weak snow at the bottom of the snowpack. 

Snowpack Summary

A big swing in temperature over the past 24 hours has likely made drastic changes to the upper snowpack. What was left of last weekend's storm snow after Monday's strong winds is now likely capped with a widespread melt freeze crust. Track the condition of the snow surface on Thursday, as it is poised to become the next sliding layer with a storm forecast for this weekend. 

Snowpack depths are variable across the region, ranging from 60 cm in eastern parts of the region up to over 100 cm in western parts of the region. Lower elevation terrain may still be below the threshold for avalanches. Reports suggest the bottom half of the snowpack consists of weak snow interrupted by a crust from early November. As last week's snow stiffens over these buried weak layers, large persistent slab avalanches may be possible to trigger.

Observations are very limited, so please submit your observations to the Mountain Information Network!

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

Problems

Persistent Slabs

An icon showing Persistent Slabs

A recent large persistent slab avalanche suggests that the snowpack may be stiffening over a buried crust that formed in early November. Large avalanches may be possible to trigger on Thursday. We have limited information about the prevalence of this snowpack structure in the region.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Dec 3rd, 2020 4:00PM