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Avalanche Forecast

Archived

Dec 19th, 2024–Dec 20th, 2024

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.
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.

Recent wind, snow, and mild temperatures led to an avalanche cycle on Wednesday.

As forecasts call for continued moderate west winds, further slab development is likely into Saturday.

The potential for natural avalanche activity remains.

Confidence

Moderate

Avalanche Summary

Wednesday's wind event following the latest storm led to a limited avalanche cycle.

Although visibility remained poor today, given the debris that is visible in the Field area, we would suspect slabs up to sz 2.5 originated in the alpine and scrubbed to the ground in the tracks.

The ski hills report triggering many wind slabs with ski cuts and explosives up to sz 2, 10 to 40cm deep. Each hill also triggered a sz 2 plus slab on the deep persistent layer with explosives.

Weather Summary

Southwest winds are forecast to remain in the moderate to strong range but shift west Friday. Treeline temperatures near -4C and scattered flurries will produce trace amounts of snow.

Terrain and Travel Advice

  • Avoid freshly wind-loaded features, especially near ridge crests, rollovers, and in steep terrain.
  • Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.