Avalanche Forecast

Issued: Dec 4th, 2011 8:39AM

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

Avalanche Canada triley, Avalanche Canada

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

The ridge of high pressure is forecast to continue to bring clear skies to the region on Sunday night and Monday. There is a temperature inversion forecast to move into the area from the Northwest. This means that it may be warmer in the Alpine than it is in the valley. This condition should be fairly short lived on Monday, and then replaced with below freezing temperatures down to the valleys by Tuesday morning. Strong South-westerly winds are forecast for Tuesday morning as a fast moving cold front move through the region. The ridge of high pressure should re-build on Wednesday, and there may be another period of above freezing temperatures in the alpine.

Avalanche Summary

No new observations have been reported. Any observations from the field are welcome. Please send to forecaster@avalanche.ca

Snowpack Summary

Expect to find around 200cm of snow near treeline. In the alpine there's either more or less depending on local wind patterns. I suspect last weekend's storm snow is settling into place and gaining strength. The snow and wind that occurred over the last few days will have created pockets of touchy windslab that will be lingering on lee and cross-loaded features at treeline and in the alpine. Forecast northerly winds may stiffen the current wind slab and/or redistribute surface snow creating new ones. A rain crust that developed on November 27th is about 20-35 cms below the surface (elevation dependant). It's about 2 cms thick at 1700m and is reportedly 'bullet-proof' closer to valley bottom. Some reactivity has been observed on this layer below treeline.Closer to the ground is the early November surface hoar; somewhere around 50 cm above ground or 150 cm below the surface. It may be difficult to trigger this layer but has a sudden planar characteristic. I also suspect a lingering rain crust down there.Finally, 2 cms of light snow fell on November 2nd burying a layer of surface hoar. It's not an issue at this point, but it's something to keep on your radarIt's still November (just barely), so we only have a teenage snowpack at best: variable, unpredictable, maybe moody. I suggest giving the snowpack a few days to reveal its secrets.

Problems

Wind Slabs

An icon showing Wind Slabs
Windslabs should be settling and becoming a bit more stubborn to trigger. Hard slabs in the alpine may propagate into large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Probability of triggering has decreased. Where it still exists, this layer may be capable of producing highly destructive, full depth avalanches. Reactivity may also increase if temperatures rise.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Dec 5th, 2011 8:00AM

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