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Avalanche Forecast

Archived

Nov 19th, 2021–Nov 20th, 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

Little Yoho.

Strong to extreme winds are forecasted for Saturday. This will likely increase the avalanche activity at upper elevations.

Weather Forecast

Light precipitation beginning Saturday will bring up to 10cm of snow to the forecast region by the end of the weekend. Strong to Extreme winds are expected at mountain top Saturday. Temperature will gradually rise this weekend with freezing levels hovering near valley bottom by Sunday.

Snowpack Summary

Several cm of fresh snow exist over a surface crust (below 2000m). Recent storm snow (5 day total of 65-90 cm) is settling. 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

Natural avalanche activity has decreased but we continue to receive report of human triggered avalanches in the region. Lake Louise ski patrol reported a remotely triggered size 2 avalanche that released on a weak layer at the bottom of the snowpack. We expect natural avalanche activity to increase with strong to extreme winds in the forecast.

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.