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Archived

Avalanche Forecast

Dec 3rd, 2012–Dec 4th, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

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 [email protected].

Avalanche Problems

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

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

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