Avalanche Forecast

Issued: Dec 8th, 2014 7:58AM

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

ccampbell, Avalanche Canada

Sea To Sky.

Warm, windy and wet weather is expected to result in natural avalanche activity and increased avalanche danger.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

On Tuesday freezing levels are expected to rise as high as 2500 m as a Pacific frontal system brings up to 60-80 mm of precipitation and extreme southwesterly alpine winds. Wednesday is looking slighly drier and cooler, but freezing levels still above 2000 m and 40-50 mm of precipitation. Thursday is looking slightly drier and cooler again with freezing levels dropping below 2000 m and another 10-20 mm of precipitation as alpine winds shift to moderate southeasterlies.

Avalanche Summary

There have been no recent reports of avalanches in the past several days; however, I suspect it may be possible to trigger new wind slabs in open leeward terrain, particularly in the alpine.

Snowpack Summary

Recent snowfall amounts vary but in some areas above 1800 m there could be 20-40 cm of moist storm snow, which has refrozen with another crust on the surface. This buried the previous snow surface of surface hoar or facetted snow in sheltered areas, which probably no longer sensitive to triggers. The midpack consists of more crusts and old facets. The snow pack depth drops significantly below treeline with essentially no snow below 1600 m.

Problems

Storm Slabs

Heavy snow and wind is expected to form weak slabs at alpine elevations. They are expected to be particularly deep and weak on Northwest-Northeast facing slopes below ridge crests.

Expect conditions to deteriorate. Assess conditions continually as you travel and be prepared to change plans.>Be alert to conditions that change with elevation and avoid wind loaded slopes near ridge crests.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

Heavy and rapid loading from snow, rain, and wind could be enough to wake up persistent weak layers and produce large avalanches.

Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

Loose Wet

Expect heavy loose wet sluffs in steep open terrain and gullies.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be aware of party members below you that may be exposed to your sluffs.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 9th, 2014 2:00PM