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Avalanche Forecast

Mar 31st, 2012–Apr 1st, 2012
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
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: South Coast.

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

Sunday: a mix of sun and cloud with light snowfall - moderate southwest winds - freezing level at 950m Monday: heavy snowfall continuing overnight - strong to extreme southwest winds - freezing level between 1000 and 1500m Tuesday: light snowfall with possible clearing - moderate southwest winds - freezing level at 700m

Avalanche Summary

Numerous natural and human-triggered slabs to size 2.5 were observed in the Duffey lake area over the last few days. The suspected sliding layer has consistently been the March 26th interface. On Face Mountain in the Railroad Pass area 2 sledders triggered a size 2 avalanche while riding the slope at the same time. The slide was 60m wide and 50cm deep and was most likely triggered on the March 26 layer. The sledders escaped without injury.

Snowpack Summary

40-60cm of new snow now 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 in sheltered areas. This week's snowfall has been accompanied by consistently moderate and at times gusty southerly winds forming windslabs in lee locations. The bonds between the new snow and this buried interface have been weak, especially in locations where the surface hoar is present. Easy planar results have been observed in testing at treeline on surface hoar size 2-4mm. At lower elevations, the consistent high freezing levels have kept the new snow moist and heavy. The deep, persistent early February layers linger in the snowpack and remain a concern with heavy triggers and rapid loading. Cornices are huge, and have continued to grow with this weather pattern.

Avalanche Problems

Storm Slabs

Recent storm snow will continue to be reactive, especially where it overlies weak layers buried on March 26th. Solar radiation may also trigger storm snow as a slab or as a loose snow avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 5

Wind Slabs

Windslabs have formed with recent snow and increased wind. They are more reactive where they overlie small, preserved surface hoar.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

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: Possible

Expected Size: 1 - 6