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Avalanche Forecast

Archived

Nov 20th, 2021–Nov 21st, 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.

Strong to Extreme winds have added more loaded to the existing problems in the snowpack. We continue to receive isolated report of large destructive avalanches.

Weather Forecast

Light precipitation forecasted for Sunday with snow accumulation amount between a trace to 5cm. Slight decrease in upper elevation winds for Sunday will be short lived as strong to extreme values return on Monday. Freezing levels will stay near valley bottom.

Snowpack Summary

Several cm of fresh snow exist over a surface crust (below 2000m).Last weeks storm snow (5 day total of 65-90 cm) continues to settle. Wind slabs exist in alpine and down into tree-line elevations. A melt/freeze crust and/or facets exist near the ground (in some locations). Snowpack depths at tree-line average 60-110 cm

Avalanche Summary

We received a report of one large size 2.5 natural avalanche observed in the Lake Louise area from the past 24 hours. This slab release was likely initiated from wind loading. local ski hills continue to report avalanches to size 2.5 triggered with explosives.

Confidence

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.