Avalanche Forecast

Issued: Mar 12th, 2012 10:08AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Tuesday: Light snowfall - strong to extreme southwest winds - freezing level at 200m Wednesday: Very light snowfall - moderate to strong south winds - freezing level at 400m Thursday: moderate snowfall - moderate to strong southeast winds - freezing level at 700m

Avalanche Summary

A skier released a size 1 hangfire slab (overburden from a previous avalanche) in the northern part of the region on Sunday. The avalanche occurred on a south aspect at 900m and is thought to have reacted on the early February interface. Most other relevant avalanche activity reported was from a natural storm cycle that occurred a few days ago.

Snowpack Summary

Continued strong and variable winds have redistributed light amounts of recent storm snow into thin wind slabs that most commonly exist at treeline and in the alpine. In the northern part of the region two persistent weak layers are on the radar of some operators: Surface hoar buried at the beginning of March is as much as 70cm deep. The early February persistent weak layers (surface hoar, facets, crusts) are over a metre down. Although not widespread throughout the region, persistent slabs would be destructive in nature and may be reactive to skier triggers, particularly below treeline on isolated and sheltered steep terrain where buried surface hoar may be preserved. Cornices in the region are reported to be very large and unstable.

Problems

Wind Slabs

Recent variable strong winds have formed thin wind slabs in unusual places, but generally below ridgecrests and in gullies.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Cornices are reported to be very large at this time. A cornice fall could be destructive by itself, and may also be a trigger for the slope below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Persistent Slabs

Operators in the North of the region are still expressing concern about early-February persistent weaknesses. Any avalanches failing on these layers could be large and destructive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 13th, 2012 9:00AM