Avalanche Forecast

Issued: Dec 21st, 2012 10:21AM

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

jfloyer, Avalanche Canada

Kootenay Boundary.

If more than 20cm new snow arrives with wind on Saturday, bump the danger ratings up by one at all elevations.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Overnight Friday: 5-10 cm new snow with strong SW winds and treeline temperatures around -6C.Saturday: Snow, picking up in intensity in the afternoon. 5-10 cm. Treeline temperatures around -4C. Winds gusting to 60 km/h from the southwest.Sunday: 5-10 cm snow expected overnight Saturday, but during the day on Sunday, things should be mostly dry. Moderate SW winds. Treeline temperatures around -6C.Monday: 5 cm new snow. Moderate SE winds. Treeline temperatures falling to -10C.

Avalanche Summary

On Friday, only loose snow avalanches to size 1 were observed.On Thursday, machine-triggered avalanches were reported running at the base of the most recent storm snow down 20 to 50 cm. Explosive testing produced avalanche up to size 2.5 in the storm snow at elevations around 2000 m.On Wednesday, natural and skier-triggered avalanches up to size 2.0 were reported to be releasing down 30-50 cms in the storm snow.

Snowpack Summary

Around 110 cm new snow has fallen in the last week. The storm slab has been very easy to trigger in areas where the wind stiffened the slab a bit. In most places the slab is still relatively unconsolidated and soft and it is not propagating far. Expect heavy sluffing in steep terrain. The well settled mid-pack has not been showing shears in snow profile tests.

Problems

Storm Slabs

With slightly warmer temperatures, the new storm may develop a denser surface slab. Recent light snow may also be transported by forecast strong southwest winds into deep wind slabs on north through east aspects.

Note recent avalanche activity.>Be cautious as you transition into wind affected terrain.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>The best powder will be found in sheltered locations at or below treeline.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Loose Dry

Loose dry snow remains unconsolidated in terrain that is protected from the wind. There is a lot of new snow; sluffing may entrain enough snow to bury a skier/rider.

Be cautious of sluffing in steep terrain.>On steep slopes, pull over periodically or cut into a new line to manage sluffing.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

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