Avalanche Forecast

Issued: Mar 2nd, 2012 9:36AM

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

Avalanche Canada pgoddard, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Saturday: Moderate to heavy snow (~15-35cm). Freezing level gradually rising to around 1500m. Strong westerly winds.Sunday: Continuing precipitation (~15-35mm). Strong westerly winds. Freezing level around 1500m.Monday: A cold front brings moderate to heavy precipitation with the freezing level dropping to valley bottom overnight as the front departs.

Avalanche Summary

Avalanche activity has slowed down over the last few days, with only sporadic reports of avalanches. However, these occurrences illustrate the unpredictable nature of persistent weak layers. On Friday, a skier triggered a size 2.5 slab very easily and very close to recent ski tracks, which failed on buried surface hoar. On Thursday, a cornice fall triggered a size 2 slab on a north aspect, which failed on the Feb 16. weakness. On Wednesday, numerous size 2-3 avalanches ran naturally, or with a remote trigger, on a variety of slopes. Most failed on an upper snowpack persistent weak layer. Natural avalanche activity is likely to increase again with this weekend's incoming weather.

Snowpack Summary

Snow is falling with strengthening winds and rising temperatures onto variable surfaces including surface hoar and facets. This is creating a nice recipe for new storm slab and wind slab instabilities. Persistent weak layers buried in February are a key concern at all elevations and could be triggered by storm slabs, wind slabs or sluffs, or with a light additional load (like you). Avalanches may be unexpectedly large, given the amount of fresh snow. Large cornices also loom as potential triggers for deep avalanches.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slab weaknesses are likely to develop as snow falls with rising temperatures. These could fail on a persistent weak layer, creating surprisingly large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 5

Wind Slabs

An icon showing Wind Slabs
Large amounts of available snow and strong westerly winds are likely to create widespread wind slabs, even at treeline. Large cornices also threaten many slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Persistent Slabs

An icon showing Persistent Slabs
Persistent weaknesses in the upper snowpack are unpredictable and tricky to manage. They may become more touchy again this weekend as storm loading and warming affects the properties of the slab above them.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 7

Valid until: Mar 3rd, 2012 8:00AM