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Avalanche Forecast

Archived

Dec 20th, 2023–Dec 21st, 2023

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

We are keeping the alpine rating elevated due to forecast winds, available snow to move, and difficulty forecasting how the basal facets will react. Cooling temperatures and calming winds this weekend may improve the danger.

Confidence

Moderate

Avalanche Summary

No new avalanches were observed or reported on Wednesday.

Snowpack Summary

Previous SW winds have created wind slabs in the alpine and exposed treeline locations. Below this is a semi-supportive mid-pack that may include a raincrust (1-7 cm thick) that exists up to 2300m. The lower snowpack is facetted and weak. Treeline snowpack amounts range from 50-90cm.

Weather Summary

A trace of snow is expected Thursday and 2cm West of the Divide. Mild temperatures continue with freezing levels rising from valley bottom to 1600-1700m in the afternoon. Alpine winds will be SW 40-50 on Thursday and 55-65 on Friday. A cold front will arrive on Friday night with a few cm of snow and cool temperatures for the weekend.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.