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Archived

Avalanche Forecast

Jan 30th, 2012–Jan 31st, 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
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Coastal.

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

A zonal flow is forecast through Wednesday with moderate to strong westerly winds and short-lived disturbances delivering 5 to 10 cm of snow each day, especially on the west (upslope) side of the ranges. Freezing level should remain near valley bottoms. Heavier precipitation is expected to start Wednesday evening when the next major system hits the coast which could bring another 30+cm by Thursday evening with freezing levels as high as 1200m.

Avalanche Summary

Reports are coming in about a widespread natural avalanche cycle that occurred on Saturday with avalanches up to Size 3.5 running almost full-path on all aspects and elevations. Natural and slope-cut activity continued on Sunday with avalanches up to Size 2 running within the upper storm snow on steep unsupported features and gullies at treeline and below. Explosive control on Sunday produced avalanches up to Size 3.5 all running on weaknesses within the recent storm snow.

Snowpack Summary

Total snowpack depths are well above average for this time of year and it won't stop snowing!Recent warm temperatures and upside-down storms created a touchy surface slab. Other weaknesses exist within and under the 150+cm of recent storm snow, but things seem so be settling rapidly. Strong winds associated with recent storms mean wind slabs on lee and cross-loaded terrain. Most snowpack concerns are limited to the surface layers, however large triggers such as cornice falls and smaller avalanche stepping-down could reawaken deeper persistent weaknesses.

Avalanche Problems

Wind Slabs

Widespread due to strong, shifting winds and large amounts of snow available for transport, but are generally lurking below ridgecrests, behind terrain features and in cross-loaded gullies. They can fail as very large, destructive avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 6

Storm Slabs

Large storm slab avalanches have been occurring for the past week and are expected to remain sensitive to triggers for the forecast period.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 6