Avalanche Forecast

Issued: Dec 25th, 2012 3:00PM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

A Pacific frontal system is expected to bring light snow accumulations starting later tonight into Wednesday. The weather pattern for the rest of the forecast period looks to be fairly benign.Wednesday: Snow amounts near 5 cm, with ridgetop winds 30 km/hr from the West and alpine temperatures near -11.Thursday: Light flurries with ridgetop winds blowing light from the West and alpine temperatures near -12.Friday: Cloudy with few sunny breaks, ridgetop winds light from the West and alpine temperatures near -10.

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. I suspect the storm slabs will still be touchy to rider triggers, especially in wind effected areas where the storm slab tends to be stiffer.

Snowpack Summary

The average storm slab depth is approximately 20 to 50 cm, and may be sensitive to rider triggers; especially in areas with wind effect on 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.
Avoid cross loaded features.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Dec 26th, 2012 2:00PM