Avalanche Forecast
Issued: Dec 4th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet and Wind Slabs.
JSmith,
Avalanche Canada
Above freezing temperatures up high over night and into the day Saturday will continue to stress the snowpack. Wet loose avalanches will be most likely to occur on solar aspects during the heat of the day.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Clear / Moderate, southwest ridgetop wind / alpine low temperature 0 / Freezing level 3000 m.
SATURDAY: Sunny / Moderate, south ridgetop wind / alpine high temperature +5 / Freezing level dropping gradually to 2000 m.
SUNDAY: Cloudy with flurries; 0-3 cm. / Moderate, southwest ridgetop wind / alpine high temperature -3 / Freezing level 1200 m.
MONDAY: Snow; 15-30 cm. / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 1500 m.
Avalanche Summary
No new avalanches were reported on Thursday.
On Wednesday, a natural widespread wet loose avalanche cycle up to size 1 occurred. A cornice failure size 1.5 also occurred triggering a small surface slab on the slope below.
As warm air and sunshine hit the region again Friday and Saturday I expect more natural avalanche activity to occur. The longer the heat sticks around the deeper it drives into the snowpack potentially initiating larger avalanches.
Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! Sending out a big thank you to the already submitted MIN's this season. Thanks everyone!
Snowpack Summary
Recent sun and warm air well into the alpine likely had the greatest impact on the upper snowpack, showing signs of instability and promoting further slab development and cohesion. This may be most concerning where these slabs sit above an old thin crust on south aspects and feathery surface hoar crystals in wind-sheltered areas. New surface hoar formation can be found on slopes where it was protected from the warm temperatures, sunshine and wind.
Northerly aspects will likely see fresh wind slab development at upper elevations on leeward slopes and melt-freeze conditions may exist especially on solar aspects at all elevations.
The snowpack depth varies with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.
The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting just above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward.
Terrain and Travel
- Avoid exposure to overhead hazards when solar radiation is strong.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Loose Wet
Rapid warming and sunshine may release loose wet avalanches. Pinwheeling is a good indicator of this type of instability.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Recent strong southerly winds have likely redistributed snow at upper elevations, building new wind slabs on leeward northerly facing terrain. The warm air coupled with solar radiation may have promoted rapid settlement and accelerated slab development in the recent storm snow on other aspects and elevations. Be especially cautious where new snow may sit over a crust (south aspects) or surface hoar (wind sheltered areas around treeline).
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 5th, 2020 4:00PM
