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Avalanche Forecast

Archived

Jan 26th, 2023–Jan 27th, 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.

Upslope snow is forecast on Friday. We are expecting 5-10 cm in most areas but may see more in eastern and southern parts of our forecast region.

Confidence

Moderate

Avalanche Summary

Sunshine and Lake Louise ski hill reported isolated, small skier controlled avalanches in wind loaded alpine and treeline features. Sunshine also noted a fresh size 2 cornice failure out of steep alpine terrain that didn't pull a slab on the slope below.

Snowpack Summary

Recent strong to extreme winds have created widespread wind effect and windslabs in the alpine and treeline. Below this, the upper snowpack contains weak layers 10-30 cm deep (Jan. 4th) and 25-50 cm deep (Dec. 17th) that are generally unreactive. The Nov 16 deep persistent layer is down 40-90 cm and continues to produce sudden results in test profiles. In areas west of the divide, these layers are generally deeper and more spread apart in the snowpack.

Weather Summary

Strong NW winds continue Thursday night until a cold front arrives and arctic air moves in. The cold front turns upslope giving more snow on the eastern and southern parts of our forecast region.

Fri: 5-10 cm snow. Alpine winds decreasing to moderate to light from the north. Temperatures cooling to -15.

Sat: Cold and partly cloudy. Alpine temps of -20 to -25. Winds light from the north.

Sun: Cold and sunny. Alpine temps -30 to -20. Winds moderate from the north.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

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.