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Avalanche Forecast

Mar 15th, 2012–Mar 16th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

Confidence

Fair - Intensity of incoming weather is uncertain on Thursday

Weather Forecast

Friday: Light snowfall - light southerly winds - freezing level at 600m Saturday: very light snowfall with a chance of intermittent sun - light and variable winds - freezing level at 300m Sunday: scattered cloud - light westerly winds - freezing level at 200m

Avalanche Summary

A size 3 natural cornice failure was observed in the region on Wednesday. Recent heli bombing in the northern part of the region produced mostly thin soft slab avalanches to size 2 that formed due to recent wind loading. With continued wind and snow throughout Thursday, I expect continued wind slab avalanche activity in the alpine and at treeline.

Snowpack Summary

Sporadic 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 triggering persistent weaknesses has become less likely, persistent slabs would be destructive in nature, 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 potentially unstable.

Avalanche Problems

Wind Slabs

Forecast strong winds and new snow will form fresh and potentially stiff wind slabs on lee slopes.

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Cornices

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

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 6