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Archived

Avalanche Forecast

Nov 23rd, 2011–Nov 24th, 2011
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Coastal.

Avalanche danger is expected to remain HIGH as long as the intense storms continue.

Confidence

Poor - Due to limited field observationsfor the entire period

Weather Forecast

Thursday: 20-30cm of snow with freezing levels as high as 900m and extreme southerly winds becoming westerly late in the day.Friday: Light to moderate precipitation increasing intensity throughout the day with 10-20cm expected by the evening. Strong westerly winds becoming extreme southerlies. Freezing levels in valley bottoms in the morning rising to 900m throughout the day.Saturday: Heavy precipitation, extreme southwesterly winds and freezing levels as high as 1000m

Avalanche Summary

No recent avalanche have been reported, but I suspect natural avalanche activity occurred and will continue in response to heavy loading from snow and especially wind.

Snowpack Summary

Another 15cm last night keeps adding to the recent storm snow total, which is now probably 70-80cm since the weekend in some areas . Varying temperature, precipitation intensity, and wind throughout the recent storms, as well as surface hoar on the previous snow surface, has probably resulted in various weaknesses within upper snowpack. The mid and lower snowpack is generally well settled and strong with an old rain crust near the ground.

Avalanche Problems

Wind Slabs

I expect wind-loading will occur well below ridge crests and behind any terrain feature, especially in cross-loaded gullies. Large natural avalanches in response to heavy wind-loading are expected.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 2 - 6

Storm Slabs

Storm slabs are likely very touchy, especially where they are sitting on surface hoar. Continued loading from new snow and rain will likely overburden weaknesses and cause natural avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4