Avalanche Forecast

Issued: Mar 3rd, 2012 9:38AM

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

pgoddard, Avalanche Canada

South Columbia.

Summary

Confidence

Good

Weather Forecast

Sunday: Moderate to heavy snow. Freezing level 500m, rising to 1100-1400m by afternoon. Strong south-westerly winds.Monday: Moderate to heavy snow. Freezing level falling in the afternoon, reaching valley bottom overnight. Light to moderate north-westerly winds.Tuesday: Light snow. Freezing level valley bottom. Light to moderate westerly winds.

Avalanche Summary

Many avalanches have been triggered remotely (from several hundred metres away) and accidentally by skiers and machinery this week. These avalanches were failing on upper snowpack persistent and storm snow weaknesses, on almost all aspects and elevations. Initial reports on Saturday indicate that a natural avalanche cycle has begun, with avalanches running near full-path and failing on a variety of aspects.

Snowpack Summary

Snow is falling with strong winds and fluctuating temperatures, creating a perfect recipe for new storm slab and wind slab instabilities. This new snow is landing on variable surfaces including surface hoar and facets. Widespread persistent weak layers buried in February have remained touchy all week and are a key concern at all elevations. Storm slabs, wind slabs and sluffs could trigger these deeper weaknesses, creating avalanches which are larger than you expect, given the amount of fresh snow. Large cornices also loom as potential triggers for deep avalanches.

Problems

Storm Slabs

Snow is falling with fluctuating temperatures, causing storm slab development. Storm slabs could step down to a persistent weak layer, creating surprisingly large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 7

Wind Slabs

Strong winds are creating widespread wind slabs, even at treeline. Large cornices also threaten many slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 6

Persistent Slabs

Touchy persistent weak layers, about 1-1.5 metres deep, are tricky to manage. These may be triggered naturally during the storm, or by a light additional load, like a sled or skier, at all elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 7

Valid until: Mar 4th, 2012 8:00AM