Avalanche Forecast

Issued: Dec 4th, 2012 9:40AM

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

jlammers, Avalanche Canada

Kootenay Boundary.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Overnight and Wednesday: Light to locally moderate snowfall overnight, easing off by Wednesday morning / Strong to extreme southwest winds / Freezing level at 1600m overnight dropping to 800m by Wednesday morning Thursday: Light snowfall / Light southwest winds / Freezing level at 800mFriday: Light snowfall / Light south winds / Freezing level at 700m

Avalanche Summary

Several natural skier triggered slab avalanches up to size 2 were reported throughout the region on the weekend. Check out the Incident Report database for a couple recent submissions. I expect much of the same with wind and snow forecast for Tuesday night.

Snowpack Summary

Up to 70 cm of moist storm snow has fallen in the past several days. This snowfall was accompanied by generally moderate to more recently strong southwest winds forming wind slabs in exposed leeward terrain. Below the storm snow you may find a layer of surface hoar or a thin sun crust that were buried on November 28th. Snowpack tests have shown easy results on this layer.In the mid snowpack, there may be a thin buried surface hoar layer between 90 and 110cm deep. At the base of the snowpack sits the early November rain crust. This layer seems most likely to be found in deeper snowpack areas at higher elevations. These layers have been unreactive in recent days, but may have the potential to 'wake-up' with continued loading and forecast warming.In general, snowpack data is sparse in this region and significant variations likely exist from one drainage to another. In short, digging down and making your own observations will be critical to safe slope selection. Any observations from the field are welcome at forecaster@avalanche.ca.

Problems

Wind Slabs

Deep and dense wind slabs are likely in exposed lee slopes and cross-loaded gullies well below ridge crests.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Storm Slabs

Instabilities may exist within or under the recent storm snow (up to 70cm) and may be triggered naturally or by the weight of a person.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

Little is known about the distribution of the November rain crust throughout the region. Although the likelihood of triggering this layer is low, the consequences could be very serious. This layer may wake-up with continued loading.

Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 5th, 2012 2:00PM