Avalanche Forecast
Issued: Nov 22nd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
Aaron Beardmore,
Forecasters are still uncertain regarding the deep persistent slab problem on the Nov 5 layer. Carefully consider big terrain, especially in the alpine.
Summary
Weather Forecast
Thankfully, the strong westerly wind will subside overnight into the moderate range. A small amount of snow, in the neighborhood of 5 cm is expected Tuesday. Potentially up to 20cm is expected on Thursday. Temperatures will remain below zero in the valley, but slightly warmer than seasonal.
Snowpack Summary
5-25 cm of fresh snow in the last two days sits on a variety of surfaces: a rain crust below 2000m, a sun crust on steep solar aspects, windslabs in the alpine and exposed treeline areas and settled snow everywhere else. Melt/freeze crusts and/or facets lurk at the bottom of the snowpack. Snowpack depths at tree-line average 60-110 cm
Avalanche Summary
Both Lake Louise and Sunshine reported wind slabs in immediate alpine lee areas up to size 2. These were triggered though various ways, ski cutting, explosive and helicopter missions. No other avalanches were observed or reported.
Confidence
Problems
Wind Slabs
Reactive windslabs exist in the alpine and down into some tree-line locations. Intense loading was observed in alpine lee areas close to Banff on Monday afternoon.
- Use caution in lee areas. Recent wind loading have created wind slabs.
- Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Although avalanches representing this problem are tapering off, forecasters are still receiving reports of them occurring. Although the latest reports are not larger than size 2, much uncertainty surrounding this problem still exists.
- Be aware of the potential for wide propagations due to the presence of hard windslabs.
- Be wary of slopes that did not previously avalanche.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Nov 23rd, 2021 4:00PM
