Avalanche Forecast

Issued: Dec 21st, 2012 9:54AM

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

Avalanche Canada ghelgeson, Avalanche Canada

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Purcells.

Summary

Confidence

Good

Weather Forecast

Saturday: Moderate SW ridge top winds diminishing after sunset. Occasional flurries. 1500m temp: -12 Freezing level: SurfaceSunday: Moderate SW ridge top winds. 1500m temp -9. Isolated flurries. Freezing Level: SurfaceMonday: Light E-SE ridgetop winds. Treeline temp -16. No snow. Freezing Level: Surface

Avalanche Summary

We're starting to see the effect of the big winds midweek.  We're getting observations from across the region of a natural avalanche cycle to size 2 in the alpine.  These avalanches are coming from steep terrain below ridgetop.

Snowpack Summary

Winds picked up mid week and moved a lot of storm snow around, especially in the upper treeline & alpine elevations. The recent storm deposited 25-50 cm in the North of the region near Golden, and 30-80 cm further South near the Purcell Wilderness Conservancy. Moderate to strong winds Wednesday/Thursday created windslabs capable of producing size 2 avalanches at and above treeline. Windslab distribution and size is wildly inconsistent across the region, but it feels like they grow in size as you travel further south.  There is some talk about a December 16th surface hoar layer, but it's distribution is *very* spotty. 

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs should slowly diminish in sensitivity this weekend, but I suspect they're still capable of failing and taking you for a ride. Watch for wind slabs immediately below ridge crest and in the lee of mid slope terrain features like ribs.
Avoid freshly wind loaded features.>Use all your senses to avoid wind affected slopes.  If you see obvious signs of wind loading, or you feel the snow stiffen under your skis or machine, back off and head to wind sheltered terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Dec 22nd, 2012 2:00PM

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