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Avalanche Forecast

Archived

Nov 21st, 2021–Nov 22nd, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Banff Yoho Kootenay.

Good ski quality exists in sheltered areas near treeline. Although we didn't have any reports of large avalanches failing on the basal facets today, we have had several over the last week. This layer demands some respect and caution.

Weather Forecast

Monday looks to be clear with strong westerly alpine winds.  The winds die down Tuesday as the next storm approaches bringing 10 -20 cm with the highest amounts in the northern part of the region. Alpine winds will remain light to moderate from the west until Wednesday. Temperatures will stay cool in the -5 to -10 range at treeline elevations.

Snowpack Summary

5-20 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

Fresh windslabs up to size 1.5 were reported from both Sunshine and Lake Louise ski hills. Today was the first day without a report of a deeper avalanche since last weeks storm, but there was limited observations due to visibility.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.