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Avalanche Forecast

Feb 24th, 2012–Feb 25th, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: South Columbia.

Confidence

Good

Weather Forecast

Tonight: Moderate snowfall (locally heavy) - 10-20cm. The freezing level (FL) should be near valley bottom. Winds shift to moderate from the NW. Saturday: Unsettled conditions with up to 15cm of snow. FL rising to 800m. Winds are moderate from the NW. Sunday: Mainly cloudy and drier. FL around 500m and winds ease to light from the NW. Monday: A mix of sun and cloud. FL near valley bottom.

Avalanche Summary

A large natural avalanche cycle occurred on Wednesday and Thursday. Slab avalanches were reported up to Size 3.5 on all aspects and at all elevations. There were also numerous reports of skier triggered and remotely triggered avalanches on a variety aspects. The potential for human triggered avalanches remains high in all terrain over 30 degrees and it may be possible to trigger an avalanche from the bottom of a slope.

Snowpack Summary

Strong and variable winds have created weak wind slabs on a variety of aspects at all elevations. Up to 80cm of new snow now sits on the February 16th Surface Hoar layer. The February 8th weakness is now down 90-120cm. This layer is a combination of weak layers: In most locations it marks a widespread surface hoar layer. On steep south & west facing aspects a sun crust that formed during the drought was also buried on Feb. 8th. This crust likely has a bit of faceting below it too, meaning that most terrain in the region has a weak layer 40-60cm under the snow surface. These buried weaknesses have made conditions very tricky with the potential for triggering in lower angle terrain and from a distance. It is should be noted that large cornices remain widespread throughout the region and may fail as temperatures fluctuate over the next few days.

Avalanche Problems

Persistent Slabs

Several buried weaknesses including surface hoar and/or a crust are ripe for triggering naturally or by the weight of a person. It may be possible to trigger avalanches in surprisingly low-angle terrain or from a distance.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 2 - 7

Wind Slabs

Dense and weak wind slabs are likely in exposed lee and cross-loaded terrain at all elevations.

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

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 3 - 8

Cornices

Cornices have grown very large. They may fail naturally, potentially triggering very large and destructive avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 3 - 8