Avalanche Forecast

Issued: Dec 20th, 2012 9:55AM

The alpine rating is moderate, 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 limited field observations

Weather Forecast

Overnight Thursday and Friday: Very light snowfall / Light to moderate southeast winds / Temperature inversion with ridgetop temperatures of -18.0Saturday: Mostly clear with trace amounts of new snow / Light southeast winds / Temperature inversion with ridgetop temperatures of -12.0Sunday: Trace amounts of snowfall / Light east winds / Ridgetop temperatures of -17.0

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.

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

Wind data in the region has been very sparse. If local wind values have been moderate or higher, smaller wind slabs may exist at higher elevations.

Assess start zones carefully and use safe travel techniques.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - 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.

Conditions may have improved, but be mindful that deep instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 21st, 2012 2:00PM