Avalanche Forecast

Issued: Dec 11th, 2012 8:58AM

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

pgoddard, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Wednesday: Moderate W winds. Alpine temp -7. Light snow. Thursday: Strong W winds. Alpine temp -7. Moderate snow (locally heavy).Friday: Light S winds. Alpine temp -7. Moderate to heavy snow.

Avalanche Summary

Large natural avalanches were heard across the valley from Shames on Tuesday. On Monday, explosives triggered several size 1.5-2.5 slabs on wind-loaded slopes north of Stewart, one of which ran on facets at the ground.

Snowpack Summary

Warm temperatures on Tuesday led to upside-down storm snow (dense snow over lighter snow) and rain at low elevations. Recent storm snow has been redistributed by very strong winds, creating wind slabs which may now be buried on a variety of slopes. Â The mid-pack is generally well-settled. A November facet/crust layer can be found near the base of the snowpack. Sporadic releases are still occurring on this layer with a heavy trigger. Above about 1000 m, the snowpack is 150-250 cm deep. Below about 1000 m, snowpack depths peter out pretty quickly.

Problems

Wind Slabs

Wind slabs are likely to be found on alpine slopes and behind ridges and ribs at treeline. Storm slabs may be lurking in areas not affected by the wind.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Deep Persistent Slabs

A deeply buried facet/crust weakness exists. While the likelihood of triggering it is low, the consequences could be a very large and destructive avalanche.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 7

Valid until: Dec 12th, 2012 2:00PM