Avalanche Forecast

Issued: Mar 21st, 2012 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs, Storm Slabs and Deep Persistent Slabs.

pmarshall, Avalanche Canada

Sea To Sky.

Summary

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.

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

Valid until: Mar 22nd, 2012 9:00AM