Avalanche Forecast
Issued: Dec 29th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
JSmith,
Avalanche Canada
A weak layer of surface hoar down 30-40 cm. has been very reactive to human triggers in the areas surrounding Valemount. This problem can be avoided through conservative terrain choices.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT: Cloudy / Light, southwest ridgetop wind / alpine low temperature -15 / Freezing level valley bottom.
WEDNESDAY: Snow; 5-15 cm. / Moderate, southwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.
THURSDAY: Cloudy with isolated flurries; 0-3 cm. / Light, west ridgetop wind / alpine high temperature -7 / Freezing level valley bottom.
FRIDAY: Cloudy with flurries; 3-5 cm. / Strong, south ridgetop wind / alpine high temperature -4 / Freezing level rising to 1200 m.
Avalanche Summary
On Sunday, skier triggered and skier remotely triggered persistent slab avalanches up to size 2.5 on north aspects at treeline and below treeline were reported just northwest of Valemount. These avalanches failed on a very weak layer of surface hoar down 30-40 cm. and the sensitivity of this layer was described as "electric"! This layer has been found to be most prevalent in the areas surrounding Valemount.
Data in this region is very sparse. Please submit your observations to the Mountain Information Network.
Snowpack Summary
Winds blowing from a variety of directions last week formed wind slabs in lee features at treeline and above.
An active weak layer is now down 30 to 70 cm. The distribution of this layer is variable. In some areas it's surface hoar and/or a crust; in others this layer may be difficult to find if it exists at all. Recent human triggered avalanches have been reported on this layer and have been most numerous in the areas surrounding Valemount.
There is a prominent crust near the base of the snowpack. This crust likely has weak facets above and/or below it. There have been no recent avalanches reported on this layer, but would be most likely to trigger in steep, shallow, rocky terrain, with a thin to thick snowpack.
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
- Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
Problems
Persistent Slabs
Recent large human triggered avalanches failed on a very weak layer of surface hoar down 30-40 cm. and the sensitivity of this layer was described as "electric"! This layer has been found to be most prevalent in the areas surrounding Valemount.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Lingering wind slabs may remain reactive to human triggers on a variety of aspects.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 30th, 2020 4:00PM
