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Avalanche Forecast

Archived

Feb 4th, 2023–Feb 5th, 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.

Wind and cornice triggered slab avalanches in the alpine have occurred daily during the past week, occasionally stepping down to deeper layers in the snowpack.

Use caution in steep lee-loaded terrain, and minimize your exposure to overhead hazards in areas where wind loading is occurring above you.

Confidence

Moderate

Avalanche Summary

Size 1-2 natural, skier and explosive triggered wind slabs have been observed every day for the past several days. Occasionally these have stepped down to deeper layers in the snowpack.

Forecasters in Yoho on Saturday were able to trigger small wind slabs on steep rolls and had shooting cracks while travelling in wind effected areas.

Snowpack Summary

5-8 cm of new snow on Saturday. Continuous moderate to strong west winds have formed new wind slabs with extensive wind effect at alpine and treeline elevations. The upper snowpack has several crusts and weak interfaces from January down 15-50 cm. The Nov 16 deep persistent facet layer is down 40-110 cm and continues to produce sudden test results. The mid and lower pack is weak in eastern regions and more supportive in western areas and along the divide.

Weather Summary

Scattered flurries on Sunday morning before a cold front moves through the region bringing 2-5 cm of snow to areas along the divide, with flurries to the East. Winds will be westerly in the moderate-strong range. Alpine high temperatures will range from 0 to -5°C with freezing levels between 1400-1600 m.

More details can be found in the Mountain Weather Forecast

Terrain and Travel Advice

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • In times of uncertainty conservative terrain choices are our best defense.

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.