Avalanche Forecast

Issued: Dec 21st, 2013 8:07AM

The alpine rating is moderate, 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 - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

Sunday: Light snowfall / Moderate southwesterly winds / Freezing level at 1200mMonday: Moderate to (locally heavy in the south) snowfall / Moderate to strong westerly winds / Freezing level at 1200m Tuesday: Broken cloud with no precipitation / Light westerly wind / Freezing level at 900m

Avalanche Summary

Several remotely triggered size 1-1.5 soft slab avalanches were observed in the North of the region on Friday. They occurred on a north/northeast aspect at treeline. The December 12th surface hoar layer was the culprit in these events.Several size 1-1.5 natural loose dry avalanches also occurred in response to recent snowfall in north facing alpine terrain.

Snowpack Summary

Snowpack depths vary greatly across the region with 130cm reported at treeline in the Northern Cascades but only 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.15-20 cm new snow now sits on a generally well consolidated snowpack. 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 very touchy surface hoar buried on December 12th sits below about 30cm of recent snowfall. This will be a weakness 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

New snow and strong ridgetop winds have created mostly isolated wind slabs in the lee of ridges and terrain breaks.

Be cautious as you transition into wind affected terrain.>Avoid freshly wind loaded features.>

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

Elevations: Alpine.

Likelihood

Possible - 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, especially with forecast snowfall.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 22nd, 2013 2:00PM