Avalanche Forecast

Issued: Dec 15th, 2011 8:12AM

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

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

A weak frontal system will move through the South Coast on Friday bringing light to moderate snowfall and rising freezing levels. Expect 5-15cm of snow, moderate SW winds, and a freezing level jumping to around 1600m. Saturday should be mainly dry during the day. The freezing level could rise as high as 2400m. Another system should move through overnight on Saturday bringing another 10-15cm through Sunday morning. The freezing level should drop to around 1200m on Sunday.

Avalanche Summary

Recent observations include several easily triggered pockets of fresh wind slab in immediate lee terrain near ridge crests. The size and likelihood of avalanches should gradually increase with incremental loading over the next few days.

Snowpack Summary

Large surface hoar and faceted powder on sheltered shady slopes, and a surface crust on sun-exposed slopes, is now lightly buried in some locations and should continue to get incrementally buried over the forecast period. Assuming the structure of this current snow surface is preserved long enough for a sufficiently thick and cohesive slab to bury it, then a highly unstable situation should develop. Particularly where surface hoar and/or faceted crystals are associated with a weak crust. Generally speaking the longer surface snow is exposed to the elements before it gets burred, the more likely it is to become a serious problem. The mid and lower snowpack are generally well settled and strong, but faceted. Basal facets and depth hoar necessitate caution on wind-exposed slopes with highly variable snowpack depths, where this deep persistent weakness could be triggered from a shallow spot. Check out the Forecaster's Blog link below for more general snowpack discussion and good advice.

Problems

Wind Slabs

An icon showing Wind Slabs
Fresh soft wind slabs may be triggered below ridge crests and behind terrain features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 16th, 2011 8:00AM

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