Avalanche Forecast
Issued: Nov 28th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Loose Dry.
Aaron Beardmore,
Uncertainty about snowfall amount Sun night into Mon. Don't be surprised if there is more than anticipated. If this is the case, the avalanche danger will be HIGH in the Alpine on Monday. Simpson and Mt Whymper CLOSED for avalanche control Nov 29.
Summary
Weather Forecast
The temperature is supposed to cool slightly and the precipitation to taper off by Monday morning. Although the wind did not materialize today, it is expected to be in the strong range from the West on Monday. Another warm wave of precip is expected Tuesday afternoon.
Snowpack Summary
35-45cm of snow since Thurs. In some locations this new snow is not bonding well to underlying hard surfaces. The Nov 15 crust is 35-60 cm down and present up to 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm.
Avalanche Summary
Lake Louise reported triggering 2 size 2 avalanches with explosives. Both slides ran on the Nov 5 crust. A size 2 was observed over Pilsner Pillar, but it was hard to determine how recent the slide was. More avalanche activity is expected on Monday, but it will depend on snowfall amounts overnight on Sunday.
Confidence
Due to the number and quality of field observations on Sunday
Problems
Storm Slabs
With lots of new snow, strong winds and rising freezing levels we expect storm slabs form in many places that will be reactive to skier triggering and may fail naturally. Treat all steep terrain with caution as the new slab builds.
- Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
With a significant new snow load we expect to see larger and more frequent avalanches occur on the basal crust and facets. These avalanches could start running full path so minimize your exposure to overhead hazards.
- Be aware of the potential for full depth avalanches due to deeply buried weak layers.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Dry
New snow and wind will result in lots of sluffing in steep gullies. If the snow turns to rain at lower elevations we could also see wet loose avalanches occur near valley bottoms. Not a good day to be traveling in confined terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Nov 29th, 2021 4:00PM
