Avalanche Forecast
Issued: Dec 14th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Dry and Deep Persistent Slabs.
Aaron Beardmore,
Wind and new snow are approaching the forecast region. Expect to see wind slab development in the alpine. Continue to watch for sluffing of surface snow in steep terrain, especially steep gullies.
Summary
Weather Forecast
The wind is supposed to pick up to the strong range on Tuesday, from the SW. Temperatures will remain steady at -15 at the ridge and about -10 in the valley. Snow is expected to start midday Tuesday and continue through until Thursday, the amount totaling about 20cm over the 3 days.
Snowpack Summary
From trace to 10cm new snow and light wind effect in the alpine. 20-40 cm of faceted snow sits on the Dec 7th layer of sun crust, facets or surface hoar depending on your location. The Nov. 5th crust / facet layer persists at the bottom of the snowpack and continues to weaken over time. Snowpack depths are 90-160cm at tree line.
Avalanche Summary
Both Sunshine and Lake Louise ski patrollers report small wind slabs up to size 1.5 at the largest, through a combination of explosive work and ski cutting.
Confidence
Problems
Wind Slabs
With forecasted strong wind from the SW on Tuesday there is a high likelihood that new wind slabs will start forming. There is a high degree of variability in the amounts of new snow for redistribution. Be watchful of this at the local level.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood
Expected Size
Loose Dry
20-40 cm of recent snow is now faceted. In steep terrain, wind or people can start a small avalanche in the surface snow that will run far on the layer of facets, sun crust or surface hoar underneath it. New snow on Tues will add to this problem.
- Be cautious with gully features.
- Be careful of loose dry power sluffing in steep terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov 5 crust has facets above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. We have only had isolated observations of a deep slab avalanches since the storm, but it is still on our minds in shallow areas.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
- Be aware of thin areas that may propogate to deeper instabilites.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 15th, 2020 4:00PM
