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Avalanche Forecast

Archived

Feb 26th, 2020–Feb 27th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
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.

Watch locally for wind slab development Thursday. Also be curious about snowpack depths as thinner areas will likely have more pronounced basal facets. Great skiing in sheltered areas.

Weather Forecast

Alpine winds at 3000m will be in the 70kmh range Thursday with 5cm of snow possible. Temperatures at treeline will range from -10 to -4C. Expect 5cm Friday and 10cm on Saturday.

Snowpack Summary

10-20 cm of recent storm snow covers previously formed wind slabs in lee areas, and buried sun crusts on steep solar aspects. The Feb 1 rain crust is down 20-50 cm and present below 1900 m. In thin snow pack areas a dense mid-pack sits over a weak, faceted base. Thick snowpack areas have a denser base with few weaknesses.

Avalanche Summary

Local ski hills reported newly formed windslab isolated to immediate lee slopes off ridge crest. Ski patrol were able to produce size 1 avalanches on this layer with ski cuts. Some large sloughs out of extreme cliffed terrain.

Confidence

Wind speed and direction is uncertain on Thursday

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.