Avalanche Forecast

Issued: Mar 21st, 2012 10:30AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

A low pressure system pushing up from the south is expected to bring 10-15 cm new snow on Thursday. Ridgetop winds are expected to be strong southerly, diminishing to moderate westerly later on. Freezing level is expected to be around 1200 m. On Friday, unsettled air behind the system may give some lingering flurries, but winds should be light and sunny breaks should start to appear. Freezing level should increase to around 1400 m. Saturday should be generally dry, with significant periods of sunshine and light winds. Freezing level expected to climb to around 1800 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

An additional 20-30cm of new snow on Tuesday with moderate to strong winds resulted in new wind slab formation in exposed leeward terrain. Several resistant shears have been noted in the storm snow. A sun crust on southern aspects and a spotty 2-6mm surface hoar on north and east aspects is down 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

An icon showing 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

Deep Persistent Slabs

An icon showing 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

Cornices

An icon showing 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

Possible - Likely

Expected Size

1 - 6

Valid until: Mar 22nd, 2012 9:00AM