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Archived

Avalanche Forecast

Mar 22nd, 2012–Mar 24th, 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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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: Kootenay Boundary.

If the sun comes out for any length of time, avalanche activity, and danger, could rapidly spike.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Friday and Saturday will stay mostly dry, with some periods of sunshine, although lingering flurries are possible. Winds should remain light. Freezing level should go to around 1600 m during the day and return to valley bottom overnight. Sunday looks bright, sunny and warm, with freezing levels going up to around 2000 m.

Avalanche Summary

A fatal avalanche incident occurred in this region on Wednesday. We will post more details when they become available. On Monday and Tuesday avalanche activity was isolated to the recent storm snow. On Sunday a large avalanche occurred in the Lumberton snowmobile area in the East Kootenays: a snowmobiler accidentally triggered a very large (Size 3+) avalanche that resulted in a close call.

Snowpack Summary

10-20 cm new snow on Wednesday night followed a previous 20-30cm of new snow on Tuesday. This new snow has built storm slabs in many places and wind slabs in exposed leeward terrain. A sun crust that recently formed on southern aspects to around 1700 m and a spotty 2-6mm surface hoar on north and east aspects are now buried around 60-100cm. Below that, the more significant early February surface hoar is down 100-180cm. Avalanche activity has become more sporadic on this layer, but ongoing large events indicate it still has the ability to fail, despite how deeply it is buried. A melt-freeze crust, down 20-30cm, below 1800m provides some bridging to the layers below. Below the early February surface hoar layer, the snowpack is strong in most places. Cornices are very large and would act as a significant trigger for all the layers mentioned above if they drop.

Avalanche Problems

Wind Slabs

Fresh wind slabs are forming on exposed lee and cross-loaded features in response to new snow and loading by SW winds.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Cornices

Cornices are very large and may fail with daytime warming, especially with sunny breaks. There is potential for triggering deep slabs on underlying slopes.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 6

Deep Persistent Slabs

The deep nature of the mid-February surface hoar layer makes potential avalanches triggered on this layer large and destructive. Avoid thin snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 3 - 8