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 Wind Slabs and Persistent Slabs.
cmortenson,
Avalanche Canada
Enjoy the best and safest riding in wind sheltered locations. Remain cautious with shallow/rocky snowpacks were it is possible to trigger buried weak layers and a large avalanche.
Summary
Confidence
Weather Forecast
Tuesday night: Mainly clear, alpine low temperatures -11C, freezing levels valley bottom & ridgetop winds moderate west.
Wednesday: A mix of sun and clouds, alpine high temperatures -6C, freezing levels valley bottom & ridgetop winds moderate to strong west/southwest.
Thursday: A mix of sun and clouds, alpine high temperatures -6C, freezing levels valley bottom & ridgetop winds moderate to strong from the southwest/west.
Friday: A mix of sun and clouds with isolated flurries, trace - 5cm new snow, alpine high temperatures -3C, freezing levels1500m & ridgetop winds moderate to strong southwest/west.
Avalanche Summary
Limited recent avalanches have been reported in recent days. On the 27th there was an explosive triggered large wind slab avalanche and loose dry sloughing to size 1 from steep terrain.
There was a large avalanche cycle last week following heavy snow falls and strong winds that included widespread large avalanches and a few very large avalanches. These avalanches were predominately wind slabs, but a few stepped down to deeper weak layers. One notable very large avalanche in a neighbouring forecast region stepped down the crust and facets at the bottom of the snow pack, highlighting the need to make conservative terrain decisions in shallow, rocky alpine snowpacks.
Please consider sharing your observations on the Mountain Information Network. Thank you to those that have already submitted this winter!
Snowpack Summary
Recent winds have re-worked snowpacks in exposed ridgecrests and alpine areas leading to scouring, cross-loading and widespread wind slabs in lee features. Wind direction has been variable, but largely from the southwest loading north and east aspects.
A crust from early December is down 40-90 cm. This persistent weak layer, with facetted crystals and surface hoar crystals above and/or below is showing signs of slowly gaining strength, as reported in this MIN from Mear Lake.
The base of the snowpack consists of a hard melt-freeze crust / sugary facets from early-November which remains on our radar.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Avoid areas where the snow feels stiff and/or slabby.
- Approach lee and cross-loaded slopes with caution.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Problems
Wind Slabs
Wind slabs are widespread from variable winds. Recent new snow may have buried these slabs. Observe wind effect like scouring, sastrugi, cross-loading and lee deposition for clues to how recent winds have reworked the terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
40-100 cm of snow currently sits above a weak layer made up of a thick crust, sugary facets , and/or surface hoar from early December. Recent avalanches have also stepped down to a crust / facet layer near the bottom of the snowpack in an adjacent forecast region.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 30th, 2020 4:00PM
