Avalanche Forecast

Issued: Dec 25th, 2013 7:59AM

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

jlammers, Avalanche Canada

South Coast.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Thursday: Moderate snowfall / Moderate southwest winds with extreme gusts / Freezing level at 1800mFriday: Light snowfall / Light southwest winds with strong gusts / Freezing level at 1300mSaturday: Mainly sunny / light winds / Freezing level at 1100m

Avalanche Summary

2 size 1.5 natural slab avalanches were observed in the Duffey Lake area on Monday. The avalanches, which occurred on north/northeast aspects at treeline, are thought to have run on the mid-December surface hoar interface. No other avalanches have been reported.

Snowpack Summary

Snowpack depths vary greatly across the region with 130cm reported at treeline in the Northern Cascades but only about 50 cm along the Duffy. In general, the snowpack across the region is significantly thinner than average for this time of year. Terrain below treeline is still mostly below threshold for avalanche activity.In the south of the region up to 25cm of snow fell on Sunday and has most likely gained significant strength. In the north of the region recent accumulations have been modest at best, although moderate to strong winds have shifted new accumulations into relatively small pockets of windslab. Previous weak interfaces within the snowpack appear generally well bonded and have been unreactive to recent snowpack tests. The exception to this seems to be in the north of the region where touchy surface hoar buried on December 12th sits about 30cm below the surface. This seems to be the interface to watch as the overlying slab develops. Early season riding hazards such as rocks, stumps and logs are lurking below the surface at treeline elevations and below.

Problems

Wind Slabs

Forecast snowfall and strong southwest winds are expected to create new wind slabs at treeline and in the alpine. Watch for more potent wind slabs in the Coquihalla area where storm accumulations are meant to be greatest.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Reports from the Duffey area indicate a touchy layer of buried surface hoar now sits under about 30cm of snow. This is likely the layer to watch as the overlying slab develops.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 26th, 2013 2:00PM