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Avalanche Forecast

Archived

Dec 16th, 2023–Dec 17th, 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 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.

Consistently strong winds have been the theme in the alpine and at treeline. Be especially warry of wind loaded slopes where ever encountered, as they likely hold touchy windslabs. As day are short, get out early and get home early.

Confidence

Moderate

Avalanche Summary

A large natural avalanche was observed yesterday in the alpine on Mount Fairview. Additionally, there have been natural, human and explosive triggered avalanches at Lake Louise and Sunshine ski hill's up to size 2 within 24- 48h. The wind slab has been the primary avalanche problem, however there are still avalanches stepping down to the deep persistent problem.

Snowpack Summary

Wind slabs have continued to build with very strong winds and recent snow. In isolated areas at treeline these slabs could be sitting on surface hoar. The early December storm has settled into a 20-40 cm layer at treeline. A rain crust up to 7cm thick exists within this storm snow as high as 2300 and is more prevalent in the south part of the region. This all overlies the deep persistent weak layers, consisting of surface hoar and basal facets. Treeline depths range from 50-90cm.

Weather Summary

Mostly cloudy skies and no new snow are forecast for Sunday. Winds are expected to decrease in intensity through Saturday night and shift to a northerly flow. Through the day on Sunday, winds should increase and shift back to a westerly flow by evening.

The alpine high is forecast at -6C and freezing levels will reach 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.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.