Avalanche Forecast

Issued: Mar 22nd, 2012 11:19AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs, Cornices and Deep Persistent Slabs.

jfloyer, Avalanche Canada

Kootenay Boundary.

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

Summary

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.

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

Valid until: Mar 24th, 2012 9:00AM