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Avalanche Forecast

Archived

Feb 20th, 2020–Feb 21st, 2020

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

Regions

Banff Yoho Kootenay.

Avoid terrain features that are/or have been loaded by alpine winds. Investigate snow depths as you travel through terrain and avoid committing yourself to shallow snowpack areas where the deep persistent layer could be triggered.

Weather Forecast

Friday will be mainly cloudy with isolated flurries and periods of sun. The temperature inversion is forecasted to weaken with an alpine high of -9. The winds will remain moderate to strong from the SW. 5-10cm of snow is forecasted throughout the day on Saturday.

Snowpack Summary

Fresh wind  slab development and continued cornice growth today in the alpine. Sun crust formation on steep S and SW facing terrain. Weak, facetted snow near the base of the snowpack persists in much of the range, producing isolated but large avalanches.

Avalanche Summary

Reports of wind slabs up to size 1.5 today along the Icefields Parkway in loaded pockets in the alpine.

A size 2.5 skier remote was reported Wednesday on the scramblers route of Cascade Mountain on a steep SW slope in the alpine, no involvement.

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.