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Avalanche Forecast

Archived

Dec 8th, 2021–Dec 9th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

Banff Yoho Kootenay.

Cool temperatures and minor amounts of new snow are keeping the likelihood of natural avalanches low, but human triggered windslabs are possible at treeline and likely in the alpine due to sustained winds transporting dry snow into leeward areas.

Weather Forecast

A NW flow will keep the weather active and temperatures cool over the next few days. Light snow expected to continue overnight Wednesday, tapering on Thursday with accumulations 5-10 cm. Temperatures for Thursday in the -10 to -15 range and sustained moderate winds from the NW. Saturday looks like a potentially big snowfall.

Snowpack Summary

5-10 cm of new snow over the last 24-hrs makes for 15-20 cm of soft surface snow above the Dec 2 rain crust. This crust disappears at about 2100 m. At treeline and above, moderate winds are developing soft slabs in immediate leeward slopes. The Dec 2 crust may cause problems in the future with additional load. Weak facets exist near the ground.

Avalanche Summary

Windslabs up to size 2 were reported by the Lake Louise ski patrol on Wednesday, formed from 36-hours of sustained winds moving snow from fetch areas. Otherwise no new avalanches reported and the last significant one was a skier accidental size 3 triggered on Lipalian Mountain (near Lake Louise) on Sunday.

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.