Avalanche Forecast

Issued: Dec 19th, 2012 8:41AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight Wednesday and Thursday: Light to locally moderate snowfall and strong southeast windsFriday: Mix of sun and cloud / Moderate to strong east winds Saturday: Mostly clear with light east windsFreezing level is expected to remain at surface for the forecast period

Avalanche Summary

On Tuesday explosives controlled slabs to size 3 were triggered in the north of the region. Some of these releases failed on basal facets. There have also been a few releases to size 2 failing within recent storm weaknesses.

Snowpack Summary

Up to 65cm of recent storm snow is settling rapidly, although weaknesses still exist within storm snow interfaces. A buried surface hoar layer, reported to be 5 to 10mm thick, recently produced sudden snowpack test results down 60-80cm in the Shames backcountry, and may exist in other areas too. Avalanche professionals continue to monitor a faceted crust near the ground. It seems this problem is confined to alpine areas and likely needs a large trigger and/or a shallow snow pack feature to trigger. Cornices are also really big and forecast strong winds and cooling temperatures could make them especially heavy and brittle.

Problems

Storm Slabs

Variable amounts of new snow will likely be sensitive to human triggers, particularly in wind-exposed terrain. Natural avalanches are possible, particularly on northwest through east aspects.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

A persistent weak layer of surface hoar, buried 60-80 cm below the surface, has been reported from around Shames. The chance of avalanche activity on this layer may increase as the slab above it gets stiffer.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

Deeply buried weaknesses exist. Large triggers, such as cornice falls, could release deeper avalanches on steep, smooth terrain, especially in thinner snowpack areas.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Dec 20th, 2012 2:00PM