Avalanche Forecast

Issued: Mar 27th, 2012 4:00PM

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

mpeter, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Wednesday: Expect flurries through the day, with southwest winds increasing to 30-50km/h. Freezing levels could reach 1800m. 15cm of snow is possible. Thursday / Friday: A series of fast-moving systems will pass through, giving short, intense flurries under moderate to strong southwest winds. Freezing levels should reach 1500m each afternoon. The most vigorous pulse is expected Thursday afternoon with 20cm possible.

Avalanche Summary

Natural and explosive triggered avalanches have been reported up to size 2.0, with the new storm snow failing on the March 26 melt freeze crust.

Snowpack Summary

The recent warm, clear weather has left us with an aggressive melt freeze crust on solar aspects well into the alpine while shady, dead north slopes have grown small surface hoar and remain powdery. In some areas up to 25cm of new snow now overlies these surfaces. New windslabs are forming at ridgecrest under the increased winds. Large cornices loom in the alpine. In recent snowpack tests, the early February surface hoar remains well preserved down 100-180cm and continues to yield sudden results. Although unlikely, triggering this layer would yield a very large, destructive avalanche.

Problems

Wind Slabs

The increased wind and new snow are forming new windslabs in lee zones at ridgecrest. These overlie a slick melt freeze crust in most locations and small surface hoar on North aspects.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Cornices are very large and will grow under the current conditions. There is potential for triggering deep slabs on underlying slopes.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 6

Deep Persistent Slabs

Triggerable from shallow areas or with a large event like a cornice fall or step down avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 8

Valid until: Mar 28th, 2012 9:00AM