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Avalanche Forecast

Archived

Dec 7th, 2021–Dec 8th, 2021

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

Regions

Little Yoho.

High winds are forecast for Wednesday morning. Watch for fresh wind slabs in the alpine.

Weather Forecast

Strong SW winds in the alpine are forecasted throughout the region for Wednesday morning. Up to 10 cm of snow is expected by the end of the day. Temperatures will remain cool.

Snowpack Summary

In the alpine conditions range from scoured, to wind effected to pockets of fresh wind slabs. The Dec 2 rain crust has formed up to 2200 m and is now covered by 5-30 cm of fresh snow depending on elevation. The lingering Nov 15 interface is down 50-100+ cm and the Nov 5 crust/facet layer is found near the ground. 90-200 cm of snow at treeline.

Avalanche Summary

No new natural avalanches observed on Tuesday. The Ski Hills reported several small explosive triggered avalanches. One significant skier accidental size 3 was triggered on Lipalian Mtn (near Lake Louise) on Sunday. This was a steeper slope in a cross-loaded, thinner snowpack area which is typical of the type of terrain to be more concerned about.

Confidence

Wind speed and direction is uncertain on Wednesday

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.