Avalanche Forecast
Issued: Dec 28th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
JSmith,
Avalanche Canada
Recently formed storm slabs will be most reactive in wind affected areas a treeline and above. Be especially cautious as you transition into wind affected terrain.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
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MONDAY NIGHT: Partly cloudy / Moderate, northwest ridgetop wind / alpine low temperature -12 / Freezing level valley bottom.
TUESDAY: Mix of sun and cloud / Light, northwest ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
WEDNESDAY: Cloudy with flurries; 5-10 cm. / Moderate, southwest ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.
THURSDAY: Cloudy with flurries; 5-10 cm. / Light, west ridgetop wind / alpine high temperature -5 / Freezing level valley bottom.
Avalanche Summary
30-50 cm. of new snow since Christmas day has buried yet another weak layer of surface hoar that was widespread at treeline and below. Expect this new snow to become increasingly reactive to human triggers as it settles into a cohesive slab.
There have been numerous recent reports of dry loose avalanches(sluffs) running surprisingly fast and far below treeline.
Snowpack Summary
30-50 cm. of new snow since Christmas day has buried yet another weak layer of surface hoar that was widespread at treeline and below. Expect this new snow to become increasingly reactive to human triggers as it settles into a cohesive slab.
Lingering wind slabs formed last week may remain reactive on a variety of aspects due to shifting winds.
Just under the new snow, down about one meter below the surface is the mid December surface hoar. This layer had been failing naturally and has been quite sensitive to human triggering throughout the storm cycle. Large avalanches have been running on this interface connecting big terrain features.Â
Below that lies the early December persistent weak layer, it's about 80 to 140 cm below the surface. This weak layer is a mixed bag that often presents as surface hoar and facets sitting on top of a supportive crust. This is a nasty weak layer, when avalanches fail on it, they have been large and destructive. Smaller avalanches in motion can step down to this one too.
Terrain and Travel
- Uncertainty is best managed through conservative terrain choices at this time.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Be especially cautious as you transition into wind affected terrain.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Problems
Storm Slabs
30-50 cm. of new snow since Christmas day has buried yet another weak layer of surface hoar that was widespread at treeline and below. Expect this new snow to become increasingly reactive to human triggers as it settles into a cohesive slab; especially in wind affected terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Smaller storm slabs in motion may step-down to deeper layers resulting in very large avalanches.
This problem can be avoided through conservative terrain choices.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 29th, 2020 4:00PM
