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Avalanche Forecast

Archived

Dec 23rd, 2022–Dec 24th, 2022

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

We have entered a period of change in the snowpack. Increased winds, warmer temps, and new snow will add load to a very weak faceted snowpack. Expect to see an increase in avalanche activity over the weekend.

Confidence

Moderate

Avalanche Summary

The Banff field team was ski-cutting newly formed wind slabs Friday. These slabs were generally 10-15cm thick and propagating up to 40m at treeline. We suspect these new slabs to be more widespread and deeper in the alpine.

Snowpack Summary

Overall, the snowpack is shallow and weak with a base of facets and depth hoar. New snow and wind have begun to create slabs of varying thickness overtop of the weak faceted snowpack. We expect these to continue to build incrementally over the weekend as the storm moves in.

Total snowpack depths at treeline range from 60-120 cms.

Weather Summary

As another weather system pushes into BC, the Westerly flow will bring a much-needed reprieve from the cold temps. Saturday we will see increased cloud cover through the day with snow accumulation beginning in the evening. Forecasted snow values range from 5 -15cm by Sunday morning. Strong to Extreme winds Saturday will likely develop new slabs on exposed features at all elevations.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • Uncertainty is best managed through conservative terrain choices at this time.

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.