Avalanche Forecast

Issued: Dec 26th, 2012 9:18AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Unsettled weather is bringing few flurries and cloudy skies overnight into Thursday morning. An upper ridge building over the coast will host a clearing drying trend, with cooler temperatures. Thursday: Cloudy with sunny breaks in the afternoon. Moderate West winds are expected and alpine temperatures near -12. Freezing levels should remain at Valley Bottom through the forecast period.Friday/Saturday: Cloudy with few flurries and some sunny breaks. Ridgetop winds will be light-moderate from the West, and alpine temperatures near -15.

Avalanche Summary

On Sunday afternoon skiers triggered a size 3.0 slab avalanche from the ridgeline off Mt. Fernie. The initial trigger was a smaller wind slab which then stepped down to a deeply buried rain crust. There were no human involvements. For further details, please visit the Incident report here:  http://www.avalanche.ca/cac/library/incident-report-database/view.No new observations from Wednesday.

Snowpack Summary

The average storm slab depth is approximately 20 to 50 cm, and may be sensitive to rider triggers; especially in areas that host more of a wind slab problem (lee slopes and behind terrain features (spines, gullies, ridgelines). Two crusts have been identified in the snowpack: one close to the ground that formed in early November and one around 90-140 cm below the surface, which formed in early December. Recent snowpack tests done on the December crust from the Harvey Pass Riding Area showed a moderate compression test failure, with a sudden collapse characteristic. The testing done on that layer showed inconsistent results. Recent compression and deep tap tests done in the Lizard Range have shown hard results. This layer may be difficult to trigger, especially in deeper snowpack areas. However, if triggered, a large and destructive avalanche would occur. The mid pack is generally well settled throughout the region.

Problems

Wind Slabs

An icon showing Wind Slabs
SW winds switching from the East have created touchy wind slabs on exposed slopes and lee of terrain features (spines, gullies and below ridgelines). Areas hosting a thinner snowpack or rocky outcrops may be susceptible larger step down avalanches.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Avoid lee and cross-loaded terrain near ridge crests.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Dec 27th, 2012 2:00PM