Avalanche Forecast
Issued: Dec 20th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
cgarritty,
Avalanche Canada
Our recent snow has been sculpted into wind slabs in exposed areas while bringing a crust layer from early December to its tipping point elsewhere. Keep choosing terrain that is unlikely to produce a shallow release and you'll avoid the potential for a nasty step-down avalanche.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT - Clearing. Moderate southwest winds.
MONDAY - Mainly sunny. Light west winds shifting northwest. Alpine high temperatures around -7.
TUESDAY - Cloudy with sunny periods. Light west winds. Alpine high temperatures around -7, warming overnight as a temperature inversion establishes.
WEDNESDAY - Sunny, with cloud increasing in the afternoon. Light south winds. Alpine high temperatures around -4, cooler at lower elevations with a light temperature inversion in place.
Avalanche Summary
Reports from Saturday continued to highlight instability of slabs that have formed above the early December rain crust. Check out this notable step-down release from the Hankin-Evelyn area.
Friday's reports likewise suggested continued snow accumulations are keeping the snowpack near the tipping point. Check out Aaron's MIN here, and this one reporting whumfing (a really important obs about deeper layers).
Thursday was also an active day. Check out Bryan's great MIN report from Hankin that outlines a few avalanche observations.
Please consider sharing your observations to the Mountain Information Network. Thank you to those that have already submitted this winter!
Snowpack Summary
Successive rounds of light to moderate snowfall have given us 30-50 cm of recent snow. This was redistributed by recent southwest winds in exposed areas but likely remains lower density in more sheltered areas.
This recent snow sits on an early-December melt-freeze crust with weak and sugary faceted grains around it. This layer has featured in several avalanche reports that can be found on the MIN.
A crust that was buried in early November is near the base of the snowpack. This crust has weak facets associated with it. These facets have produced large avalanches in both the south and north of the region. Friday's reports of whumpfs suggest this layer should still play a role in guiding your terrain selection.
Snowpack depths vary substantially with aspect, elevation, and wind exposure.
Terrain and Travel
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
30-50 cm of recent snow has been forming widespread slab problems. This may present as a wind slab issue in specific terrain at higher elevations, but sheltered lower elevations aren't exempt. In many instances storm slabs have been running on a buried crust from early December. Slabs have been seen triggering very easily on wind loaded slopes.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Weak faceted grains near the base of the snowpack have the potential of forming large and destructive avalanches. The most likely place to trigger this layer would be on shallow and rocky slopes. Smaller avalanches may also have the potential of stepping down to this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 21st, 2020 4:00PM
