Avalanche Forecast

Issued: Mar 21st, 2012 10:46AM

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

Avalanche Canada pgoddard, Avalanche Canada

Be wary of any slopes receiving direct sun. Solar warming could trigger avalanches or weaken existing slabs.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

Thursday: Light snow. 5-10cm. Light to moderate south-west winds. Freezing level at valley floor.Friday/Saturday: Clear and sunny. Light winds. Afternoon temperatures rising on sunny slopes, with the freezing level falling to valley floor at night.

Avalanche Summary

On Tuesday, little activity was reported, except a size 1 storm slab which was triggered by a skier. On Monday, natural avalanches up to size 3.5 failed on southerly aspects down about 100-150cm on the mid-February persistent weak layer. Avalanches releasing on this layer are becoming less frequent. Solar warming is of particular concern over the next few days, as it could destabilize storm slabs and cornices, potentially initiating deep failures on the mid-February layer. Be particularly wary of sunny aspects during the heat of the day.

Snowpack Summary

15-30cm of recent storm snow overlies various surfaces including settled snow, wind slabs and crusts. New wind slabs have formed in the alpine and at treeline. Sunny breaks on Sunday caused moist snow up to about 2400m on solar aspects and up to about 1500m on all aspect. Cornices have grown large and unstable. The new snow has added to the well consolidated storm slab that overlies weak surfaces that formed early February. This interface, which lies 1-2m below the surface, includes a widespread surface hoar instability that, depending on aspect and elevation, may exist in combination with facets or crusts.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs in the alpine and at treeline may take a few days to settle and bond. Cornices are very large and also threaten slopes below.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Storm Slabs

An icon showing Storm Slabs
Storm slabs are most likely to be triggered from steep or convex terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The mid-February weak layer of facets, surface hoar, and crusts has been buried for about six weeks. While they are becoming less frequent, avalanches that do release on this layer may be very large and destructive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 8

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