Avalanche Forecast

Issued: Mar 18th, 2012 10:22AM

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

pgoddard, Avalanche Canada

Sea To Sky.

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Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

Monday: Mainly sunny. Cloud increasing and snowfall starting in the evening. Light winds. Tuesday: Moderate to heavy snow. Freezing level near 400m. Strong south-westerly winds.Wednesday: Scattered convective snowfall. Light winds.

Avalanche Summary

Last week was very active with natural avalanche activity, human involvements and close calls. Some were failing on the mid-February persistent weakness. The size and frequency of avalanches seems to have decreased slightly over the weekend as storm slabs and wind slabs slowly gained some strength. On Sunday, avalanches were triggered naturally and by explosives in steep, rocky terrain to size 2. Avalanche activity may increase again with solar warming on Monday, or with snow and wind on Tuesday.

Snowpack Summary

Last week, 100-180 cm storm snow fell, accompanied by strong south-easterly to south-westerly winds. Storm slabs and wind slabs now appear to be slowly gaining strength. 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 350 cm.

Problems

Storm Slabs

Recent storm snow is deep and variable, and may not have fully settled. Storm slabs may fail naturally if exposed to direct sunshine.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 6

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

Possible - Likely

Expected Size

1 - 6

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 19th, 2012 9:00AM