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 Deep Persistent Slabs.
ahanna,
Avalanche Canada
As a pocket of above-freezing air re-establishes in the alpine, we may see a renewal of loose wet avalanche activity especially on steep sun exposed slopes at upper elevations. Make observations as you travel and be ready to back off your line if the snow is getting cooked.
Summary
Confidence
Moderate - Uncertainty is due to rapidly fluctuating freezing levels. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack. Uncertainty is due to the limited number of field observations.
Weather Forecast
Friday night: Clear, light southwest wind, strong temperature inversion with above freezing air 1800-3000 m.
Saturday: Sunny, light southwest wind, strong temperature inversion with above freezing air 1800-3500 m.
Sunday: Sunny, light southwest wind, freezing level 800 m.
Monday: Increasing cloud with flurries starting in the afternoon, light to moderate southwest wind, freezing level 800 m.
Avalanche Summary
Loose wet avalanches up to size 2 were reported on steep solar aspects during the warmup on Wednesday, and to a lesser extent on Thursday.
Our eyes and ears in the mountains are limited this winter due to fewer professional observations. If you go out in the mountains, please share your observations on the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!
Snowpack Summary
A melt-freeze crust on steep solar aspects at treeline and above will soften through the day. On shadier aspects, alpine surfaces are predominantly wind affected, with soft snow still to be found in at lower elevations. Widespread growth of large surface hoar crystals and surface faceting have been reported. These types of crystals (crust, hoar, facets) that develop on the surface as it sits exposed during prolonged periods of high pressure like this often become a problem once buried by the next snowfall.
A couple of layers of feathery surface hoar crystals exist in the upper snowpack. Just 10 cm below the surface, the first of these layers has likely broken down in areas where the surface warmed up on Wednesday. Another patchier layer of smaller crystals may sit beneath 20-40 cm of old wind slab.
The lower snowpack is characterized by a couple of crusts, the most notable of which is sitting near the base of the snowpack, likely surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky areas in the alpine.
Terrain and Travel
- Make observations and assess conditions continually as you travel.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Avoid exposure to overhead hazards when solar radiation is strong.
Problems
Loose Wet
Watch for loose wet avalanche activity especially on steep sun exposed slopes in the afternoon. Pinwheeling is a great indicator of a warming snowpack.
Aspects: East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A crust sits near the base of the snowpack. Although we haven't had any reports of avalanche activity on this layer during the ongoing warming event, there is potential for large avalanches to be triggered on this layer by:
- large loads such as cornice falls or smaller loose wet avalanches
- human traffic in thin, rocky areas in the alpine
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 5th, 2020 4:00PM
