Avalanche Forecast

Issued: Dec 18th, 2012 9:19AM

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

pgoddard, Avalanche Canada

South Coast.

Conditions are variable across the region. The Coquihalla has received the deepest amounts of storm snow and conditions are likely to be touchier there than elsewhere. Danger ratings reflect the Coquihalla area conditions.

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

Wednesday: Strong to gale S winds. Alpine temp -10. Moderate snow (~20 cm).Thursday: Moderate S winds. Alpine temp -9. Light snow.Friday: Cloudy and cool. Very light snow possible.

Avalanche Summary

Size 1-2 sluffs were running in steep terrain on Sunday and Monday. On Sunday, skiers were also triggering numerous size 1 soft wind slabs. Near the Coquihalla summit, skiers triggered a slab at treeline which was at least 100 m wide and ran about 150 m downhill before stopping in the trees. One soft slab at treeline in the Duffey Lake area failed on a layer of stellars and surface hoar down 30 cm.

Snowpack Summary

Expect new storm slabs and wind slabs to form on Wednesday. Previous low density storm snow has been shifted by variable winds into soft slabs in the alpine and at treeline. A layer of surface hoar and stellars buried on Dec 10 exists at treeline in the Duffey Lake area and may be more widespread. Recent snowpack tests produced hard to no results on a deeper surface hoar layer from late November, buried down 70-100 cm. A consolidated mid-pack overlies the deeply buried November crust/facet layer, which continues to give occasional sudden planar compression test results. This layer has not been observed in the Coquihalla area.

Problems

Storm Slabs

Further new snow and strong winds are likely to create many instabilities. Be alert for wind slabs behind ridges and ribs and soft slabs or sluffs on steep terrain sheltered from the wind.

Avoid convexities or areas with a thin or variable snowpack.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Valid until: Dec 19th, 2012 2:00PM