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Archived

Avalanche Forecast

Mar 1st, 2012–Mar 2nd, 2012
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
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
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: South Columbia.

Conditions are highly variable across the region.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Friday: A brief ridge of high pressure brings dry, stable and cool conditions until the afternoon, when the next weather system approaches, bringing moderate snowfall overnight, especially to the north of the region. Saturday/Sunday: Moderate snow in the north and west, with less in the south. Each day, about 20cm or so is forecast near Revelstoke, and about 10cm further south. Strong westerly winds all weekend. Freezing level gradually rising and peaking at 2000m on Sunday.

Avalanche Summary

Avalanche activity has begun to slow, with avalanche size and frequency decreasing. However, a number of avalanches are still being triggered remotely (from several hundred metres away) and accidentally by skiers and machinery. These avalanches are failing on upper snowpack persistent and storm snow weaknesses, on almost all aspects and elevations. Human-triggering of destructive avalanches remains a distinct possibility, while in-your-face clues of instability have diminished. Avalanche activity is likely to increase again this weekend with incoming weather.

Snowpack Summary

In the west and south, 10-15cm of snow fell overnight Wednesday, which may have created localized new storm slabs. For the rest of the region, 60-140cm of recent storm snow is slowly settling above the Feb 16. surface hoar layer and the early Feb interface. A storm snow weakness down about half a metre is touchy in some areas. The early Feb interface consists mainly of surface hoar (widespread) or a melt-freeze crust (on solar aspects). These layers are still touchy, with remote triggers reported each day and full propagation in snowpack tests. It is challenging to pin down exactly where you are most likely to trigger these persistent weaknesses. Wind slabs are now buried by a few cm of snow and bury the upper snowpack weaknesses deeply in places. Large cornices loom as potential triggers for deep avalanches.

Avalanche Problems

Persistent Slabs

Several weaknesses exist in the upper metre or so of the snowpack. Large, destructive avalanches could be triggered by the weight of a person, even from a distance.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 7

Storm Slabs

A storm snow weakness down about half a metre may still be touchy, especially on steep or convex terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 4

Wind Slabs

Variable wind slabs are now buried by new snow. Persistent weak layers are buried beneath these slabs, meaning they could step down to create very large avalanches. Large cornices also threaten many slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 5