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Avalanche Forecast

Mar 21st, 2012–Mar 22nd, 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
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
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Confidence

Fair - Due to variable weather conditions

Weather Forecast

Thursday: Cloudy with flurries - 2-5cm. The freezing level rises to around 800-1000m during the day. Winds are light and variable. Friday: A mix of sun and cloud. Freezing level staying low near 800m. Winds remain light. Saturday: Mainly sunny and milder with the freezing level jumping to 1500m. Winds are light from the southeast.

Avalanche Summary

Avalanche control on Tuesday produced numerous small slab avalanches (10-30cm deep) and a couple slabs up to Size 2, primarily in wind loaded terrain near ridge top. On Monday, a skier triggered a buried wind slab on a convex roll 30-40cm deep on a north-east aspect. Some natural activity was also observed on steep solar aspects.

Snowpack Summary

Snow and wind created fresh wind slabs and storm slabs on Tuesday. Heavy snow which fell last week is slowly settling, but variable storm snow weaknesses and buried crusts mean a deep storm slab release is still possible. Cornices are large and threaten slopes below. A persistent weakness, formed in mid-February, continues to produce hard, sudden planar results in snowpack tests. The likelihood of triggering this layer has gone down, but very large avalanches remain possible, which could be triggered by a shallower avalanche or cornice fall. The average snowpack depth at treeline is 350cm.

Avalanche Problems

Wind Slabs

Wind slabs lurk below ridges, behind terrain features and in gullies. They may be buried by new snow, making them hard to spot.

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Storm Slabs

Variable new and old storm slabs could be triggered on steep or convex terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Persistent weaknesses still have the potential to create very large, destructive avalanches if triggered. Possible triggering mechanisms include a person/sled on a thin snowpack spot, cornice fall, or step-down avalanche.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 4 - 8