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Avalanche Forecast

Archived

Feb 13th, 2023–Feb 14th, 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.

Skiers and explosives continue to trigger the windslab and deep persistent problem layers. Stick to lower angle and well-supported terrain. Give the snowpack time to adjust to the recent loads.

Confidence

Moderate

Avalanche Summary

Although the peak of the cycle has passed, there have been more skier and explosive-triggered avalanches on Monday. Skiers triggered a size 2 windslab on the convex roll in Wawa bowl near Sunshine Ski area. Avalanche control on Mt. Dennis and Mt. Field on Monday produced results up to size 3. These avalanches failed at the ground in the deep persistent basal facets in terrain that had been previously controlled.

Over last weekend there were several notable avalanches. Bourgeau Left hand slid naturally (size 3). On Saturday there was a MIN report of a remote-triggered slide with wide propagation in the Sunshine backcountry. On Sunday, a visitor safety team also triggered a healthy size 2.5 (80 wide) at 2400m on observation glades and another party on Helen Shoulder triggered a size 2.

Snowpack Summary

Up to 40cm 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

Tuesday, expect scattered flurries, more along the East slopes with up to 5 cm in some locations, and N-NW wind at 20-30 km/hr. Temperatures will range from -5 to -11 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • 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.