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Avalanche Forecast

Archived

Dec 11th, 2023–Dec 12th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

The natural avalanche cycle over but human triggered avalanches are still likely. Continue to practice conservative decision making.

Confidence

Moderate

Avalanche Summary

On Saturday a size 2 skier triggered avalanche failed as a deep persistent slab at treeline and ran 600m scrubbing to ground. One skier was caught and sustained injuries that required an overnight rescue.

Numerous Na slab avalanches up to size 2 have occurred in the alpine over the past few days.

Snowpack Summary

Last week's storm snow has settled to 20-50cm over the Dec 2 weak layer which consists of the basal facets and surface hoar. A rain crust (1 to 7cm thick) exists within the storm snow up to 2300m on all aspects. The thickness of the rain crust tapers with increasing elevation.

Weather Summary

Tuesday will be mainly sunny with light southwest ridgetop winds and a temperature inversion, alpine highs of -6°C to -3°C. Wednesday will be much the same with increased winds and slightly higher freezing level. The next potential for snow is Thursday.

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

Problems

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.

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.