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Avalanche Forecast

Feb 9th, 2012–Feb 10th, 2012
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Rockies.

Confidence

Good - -1

Weather Forecast

A series of weak frontal systems are expected to bring light amounts of fresh snow to the region on Friday, and trace amounts for Saturday and Sunday, but the timing is uncertain. Winds are expected to be generally light southwesterlies, but winds associated with snow squalls could get quite gusty. Freezing levels should remain in valley bottoms but could rise above 1000m with the passage of warm fronts.

Avalanche Summary

Throughout the weekend numerous highly destructive persistent deep slab avalanches involving basal facets and depth hoar occurred in the alpine and ran to valley bottoms (check out the Avalanche Image Gallery under the Library tab for some photos). These highly destructive avalanches remain possible with heavy triggers, such as airborne sled impacts and cornice falls, in thin areas on variable slopes peppered with tree's and rocks.

Snowpack Summary

In Elk Valley North and the Crowsnest, the average snowpack depth at treeline is 150 cms. In Elk Valley S and the Flathead the snowpack depth is closer to 2 m. Surface hoar is continuing to develop on sheltered slopes at all elevations combined with near-surface facets at lower elevations and surface crusts on sun-exposed slopes. A well settled and strong snowpack sits on weak basal facets and depth hoar, which seem to be fairly widespread throughout the region. This deep persistent weakness recently became active again with warm temperatures, but cooler temperatures have once again reduced the sensitivity to triggers. Highly unpredictable glide cracks are also opening up, primarily on slopes with smooth ground cover. These full-depth gaping 'crevasses' could release without warning or act as a significant terrain trap.

Avalanche Problems

Wind Slabs

Fresh wind slabs are expected to develop below ridge crests and behind terrain breaks in lee and cross-loaded terrain.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3

Deep Persistent Slabs

Deep and destructive persistent slabs have become less likely, but may be triggered with a large trigger (cornice fall, trenching sled); especially in unsupported, rocky terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6

Cornices

Cornices are large, unsupported and may be a trigger for a large avalanche on the slope below.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3