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Avalanche Forecast

Archived

Feb 12th, 2023–Feb 13th, 2023

Alpine
Natural and human triggered avalanches likely.
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.

Strong to extreme winds with new snow will keep the avalanche hazard elevated. An avalanche cycle in the alpine is possible early Monday, depending on new snow amounts.

Avalanche control will take place Monday, Feb 13 on Mounts Field, Stephen and Dennis in Yoho National Park. No activities on these peaks for the day.

Confidence

Moderate

Avalanche Summary

A busy 24 hours for avalanches. Bourgeau Left hand slid naturally (size 3) in the last 24 hours, and explosive control triggered wind slabs to size 2. A MIN report from Saturday of a remote-triggered slide with wide propagations in the Sunshine backcountry. A visitor safety team also triggered a healthy size 2.5 (80 wide) at 2400m on observation glades on Sunday.

Snowpack Summary

Up to 30cm of recent storm snow in the North (10cm in the South) of the region has been redistributed by strong winds forming widespread, reactive windslabs. Two crusts exist in the upper snowpack and the November facets remain near the base. These buried weak layers remain a concern and continue to produce avalanches. Minimal reactivity has been observed below treeline.

Weather Summary

Strong to extreme alpine SW winds can be expected overnight into Monday (70-90km/h). North of Lake Louise 15-20cm is possible, with lower amounts to the East. Snow will taper by the afternoon as winds die down. Freezing levels will remain at valley bottom and alpine temperatures -3 to -9C. Cooler temperatures and light winds for Tuesday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.