Avalanche Forecast

Issued: Dec 19th, 2012 8:32AM

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.

jlammers, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight Wednesday and Thursday: Light snowfall and strong southeast winds. Winds are expected to become light by Thursday.Friday: 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

No recent avalanches have been reported. On Wednesday last week, a snowmobiler triggered a hard wind slab at the Sinclair riding area. It failed on the November crust/facet layer 30 cm above the ground while side-hilling. Check out this incident report for more details. This deep crust/facet layer has been the failure plane for a number of large avalanches further to the west and was suspected to have failed at the Hankin-Evelyn area last weekend.

Snowpack Summary

Light amounts of new snow overlie older storm and windslab instabilities which are likely settling and gaining strength. Spotty surface hoar was buried in the upper snowpack, particularly in sheltered treeline areas. Of key concern is a November facet/crust layer which can be found near the base of the snowpack. This layer, which is widespread, can be triggered from thin-spot trigger points, or with a heavy load, such as storm slabs stepping down, a cornice fall or a snowmobile track digging a trench. It has the potential for large, destructive avalanches. In general the snowpack depths, and therefore strength is highly variable due to windy conditions this season.

Problems

Wind Slabs

Be alert for new wind slabs in the lee of ridges and ribs.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

A deeply buried facet/crust weakness exists. This layer could be triggered by large loads, such as a cornice collapse or a rider digging deeply with a spinning track in a shallow spot on a steep, slope.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

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