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Avalanche Forecast

Archived

Dec 19th, 2023–Dec 20th, 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 possible, human triggered probable.
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.

Ridgetop winds are forecasted to pick up over the next few days, although previous winds have already moved much of the available snow. Pay attention to wind loading as you make your way into the alpine and continue to make conservative terrain choices.

Confidence

Moderate

Avalanche Summary

Lake Louise Ski Area reported triggering some small windslabs in alpine terrain with explosives on Tuesday. Otherwise, no new avalanches observed or reported.

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.

Weather Summary

Light flurries with minimal accumulation are forecasted along the continental divide through Friday. Ridgetop winds will be SW, moderate to strong on Wednesday, picking up to strong to extreme on Thursday, and then easing slightly to strong on Friday. Temperatures will be relatively mild with freezing levels near valley bottom.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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.