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Archived

Avalanche Forecast

Nov 26th, 2011–Nov 27th, 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
4: High
The avalanche danger rating below treeline will be high
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.

A series of strong frontal systems will affect the region resulting in HIGH avalanche danger throughout the forecast period. Travel in avalanche terrain is not recommended.

Confidence

Fair - Due to limited field observations

Weather Forecast

Snow should ease off on Sunday morning with a freezing level lowering to around 500-600m. Winds should be light to moderate from the W-SW. Another frontal system arrives on Monday bringing heavy snowfall and rising southwesterly winds to most areas through Tuesday morning. 40-70cm of snow is possible with a freezing level around 700m. Precipitation should ease off by Tuesday afternoon.

Avalanche Summary

Recent reports are limited to the highway corridors near Bear Pass and Terrace. Several natural avalanches up to Size 3 were observed, primarily in response to strong westerly winds. Explosive control produced a few Size 2-2.5 avalanches involving the recent storm snow. Both natural and human triggered avalanche activity should remain likely throughout the forecast period.

Snowpack Summary

Heavy snowfall continued on Saturday with some areas reporting more than 50cm of snow by mid-day. The snowpack depth near treeline is already around 300cm. Fluctuating freezing levels and varying precipitation intensity and wind throughout the recent storms has probably resulted in various weaknesses within upper snowpack. Widespread surface hoar was also observed on the previous snow surface at all elevations, but there is no recent information on this layer. The mid and lower snowpack is generally well settled and strong with an old rain crust near the ground.

Avalanche Problems

Storm Slabs

Weaknesses may exist within or under the recent storm snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 2 - 5

Wind Slabs

Expect to find deep and dense wind slabs in exposed terrain well below ridge crests.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 2 - 6