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Archived

Avalanche Forecast

Apr 2nd, 2012–Apr 3rd, 2012
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
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
1: Low
The avalanche danger rating below treeline will be low

Regions: South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

The big story for the forecast period is an intense frontal system lined-up to hit the Coast on Monday night. WInds will be in the strong to extreme range with heavy snow accumulations. Tuesday: light snowfall - strong south winds decreasing to moderate throughout the day - freezing level at 1100m Wednesday: very light snowfall - light southwest winds - freezing levels at 1100m Thursday: Mix of sun and cloud as a clearing trend develops - light north winds - freezing level at 1200m

Avalanche Summary

On Sunday, numerous natural windslabs to size 1.5 were observed at treeline and above in the Duffey Lake area. With weather forecast for Monday night, expect widespread windslab and storm slab avalanche activity with potential to involve the deeper March 26th layer.

Snowpack Summary

Recent light snow accumulations add to the 40-70cm of snow that fell over the past week. Winds have mostly been moderate with strong gusts forming windslabs in lee locations. The past week's snowfall overlies an interface that was buried on March 26. This interface consists of a crust that exists on all aspects and elevations except north facing slopes at treeline and above where small surface hoar (5mm) may be found. The bonds between the new snow and the March 26th interface have been weak, especially in locations where the surface hoar is present. In the north of the region, persistent early February layers linger deeper in the snowpack and remain a concern with heavy triggers and rapid loading. Cornices are huge and potentially very destructive.

Avalanche Problems

Wind Slabs

Forecast strong to extreme winds and heavy snowfall will form reactive and potentially destructive new wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 5

Storm Slabs

Forecast heavy snowfall will add to an ongoing storm slab problem. Storm slabs will be more destructive than usual if they fail on weak layers buried on March 26th.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 6

Cornices

Large cornices loom at ridgecrest and will continue to grow with forecast weather. A cornice fall could be destructive by itself, or may act as a trigger to deeper weaknesses on the slope below.

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

Elevations: Alpine.

Likelihood: Likely

Expected Size: 1 - 6