Avalanche Forecast

Issued: Dec 3rd, 2012 8:26AM

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

Avalanche Canada Peter, Avalanche Canada

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Synopsis: A frontal system will move through southern BC on Tuesday bringing moderate snow, very strong winds, and rising freezing levels. Unsettled and cooler conditions are expected in the wake of this system.  Tuesday: Moderate snow – 15-20 cm; the freezing level could jump to 1600-1800 m; winds are very strong from the southwest. Wednesday and Thursday: Cloudy with flurries; the freezing level lowers to 600-800 m. 

Avalanche Summary

Several natural and skier triggered slab avalanches up to size 2 were reported throughout the region on the weekend. Most of these avalanches were 40-50cm deep and involved the recent storm snow. Check out the Incident Report database for a couple recent submissions. I expect much of the same for Tuesday with forecast snow, strong winds, and warming.

Snowpack Summary

Up to 70 cm of moist storm snow has fallen in the past several days. This snowfall was accompanied by generally moderate south-southwest winds, forming wind slabs in exposed leeward terrain. Below the storm snow is a layer of surface hoar or a thin crust. Recent snowpack tests give consistent easy results on this layer.In the mid snowpack, there may be a thin buried surface hoar layer between 80 and 100cm 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

An icon showing Wind Slabs
Deep and dense wind slabs are likely in exposed lee slopes and cross-loaded gullies well below ridge crests.
Avoid lee and cross-loaded terrain near ridge crests.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Storm Slabs

An icon showing 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.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Stick to simple terrain and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Although the likelihood of triggering this layer is low, the consequences could be very serious. This layer may wake-up with continued loading.
Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 4th, 2012 2:00PM