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Avalanche Forecast

Archived

Dec 8th, 2023–Dec 9th, 2023

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

Regions

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

Up to 60+ cm of recent storm snow will take time to settle over the weaker basal layers. A spike in wind starting Saturday afternoon will be a factor in keeping the danger elevated.

Confidence

Moderate

Avalanche Summary

Avalanche control Friday produced results to size 2.5. Most were observed initiating on the basal facets, but it is unknown what layers many slid on. As skies clear, there are more observations of natural avalanches from the last few days. Most are up to size 2.5, failing on or near the ground.

Snowpack Summary

Up to 60 cm of storm snow overlies the Dec 2 layer of surface hoar, facets and a crust. Below this layer are basal facets and a crust formed in late October. We suspect there is some separation between these weak layers in the alpine, but at treeline and below, they are essentially the same layer. Snow depths range from 80-100 cm at treeline and up to 140cm observed in alpine locations.

Weather Summary

Winds will increase mid-day Saturday in the alpine to strong, starting NW and switching to SW. Temperatures will cool to -14 to -16 with mainly sunny skies. A trace of snow on Sunday with continued strong winds.

For more information, click Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.

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.