Avalanche Forecast

Issued: Dec 16th, 2012 9:14AM

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.

Danger ratings are set for the Coquihalla, where recent storms have been focussing heavy snow. Conditions in the rest of the region are less touchy.

Summary

Confidence

Fair - Due to variable weather conditions

Weather Forecast

Sunday night: Moderate SE winds. 5-10 cm snow (locally up to 30 cm around the Coquihalla). Freezing level at surface.Monday: Strong winds changing from SE to W. Alpine temp lowering to -10. A few cm snow.Tuesday: Light to moderate SE winds. Alpine temp -7. Very light snow. Wednesday: Light SE winds. Alpine temp -11. 20 cm snow.

Avalanche Summary

There were a few reports of small natural and human triggered loose snow avalanches, and isolated thin wind slabs immediately lee of ridge crests late last week. Previous reports include evidence of large avalanches, including one from Mt Joffre at 2000m and the east face of Cayoosh Mountain in the Duffy Lake area last weekend (check out Wayne Flann's Avalanche Blog for a photo of the Cayoosh avalanche).

Snowpack Summary

Deep new snow affected the Coquihalla much more than other parts of the region over the weekend. The next system forecast to arrive overnight Sunday/Monday is likely to follow the same pattern. This means that storm slabs and wind slabs will probably be more widespread around the Coquihalla than elsewhere. New snow may have buried a thin layer of surface hoar in some areas. Moderate westerly winds are likely to have created wind slabs in lee terrain. The late November surface hoar down 70-130 cm produces inconsistent results with snowpack testing. A well settled and rounding mid-pack is overlying 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.

Problems

Storm Slabs

New snow and changing winds will continue to build touchy slabs which could be triggered naturally, or by the weight of a skier or snowmobile. This problem is likely to be worst around the Coquihalla, where the most intense snowfall is expected.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Valid until: Dec 17th, 2012 2:00PM