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Avalanche Forecast

Archived

Feb 19th, 2020–Feb 20th, 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.

Watch for local wind loading Thursday especially in gully features and near ridge crests. Shallow (under 150cm) snowpack areas have very prominent basal facets and depth hoar.  Terrain choice is the best defense against this problem.

Weather Forecast

A temperature inversion (warmer in the alpine, colder in the valley) will start to break down Thursday bringing with it increased winds which will be in the strong range (up to 80kmh) in the alpine. Temperatures will be in the -10C range but likely colder in the Louise region in the AM. No snow is forecast in the next 24 hours.

Snowpack Summary

Continued settlement and cool temperatures are slowly stabilizing the recently formed windslabs, which could still be triggered in steep, loaded areas in the alpine. Some 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

No new avalanches today.  There was a report yesterday of a size 2.5 wind slab that was triggered by ski tourers on the scramblers route of Cascade Mountain.  It was on a steep SW slope in the alpine with 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.