Avalanche Forecast

Issued: Dec 1st, 2013 8:16AM

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

Avalanche Canada rbuhler, Avalanche Canada

Storm snow amounts vary across the region. Avalanche danger at Treeline and Below Treeline may be higher in areas with above average snowfall.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

The low pressure system which caused winter storms over the weekend will be replaced by an arctic front on Monday. This arctic front will result in clear, cold, and dry conditions over the interior regions.Monday: Light snowfall in the morning, increasing sun in the afternoon, decreasing temperatures during the day, and moderate to strong alpine winds from the NE as the arctic front approachesTuesday/Wednesday: Mostly sunny, no precipitation, light NE winds, and unseasonably cold conditions.

Avalanche Summary

No recent avalanches have been reported but incoming field data is still very limited.

Snowpack Summary

Variable snowpack depths are being reported across the region but typically 30-50 cm of storm snow has fallen on approximately 1m of old, well-settled snow. The new storm slab will increase in reactivity and destructive potential as it deepens or in areas where it has been redistributed and compressed by wind. The storm slabs are forming over a variety of old snow surfaces including (1) winds slabs and wind scoured areas in the alpine and exposed areas at treeline, (2) sun crusts on steep south facing slopes, and (3) surface hoar in sheltered areas around treeline elevation and below. There are still two layers of concern within the mid/lower snowpack: the early November surface hoar is down roughly half way (50-60cm) and the October rain crust is near the ground. While these layers have recently become dormant, the weight of the new storm snow may cause these layers to reactivate in isolated areas causing large, destructive avalanches. The October crust can be found in the alpine on north aspects (likely east and west as well). The early November surface hoar appears to be spotty and drainage specific.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm snow may be sitting on the late November surface hoar/sun crust interface. In windy alpine areas, stiffer wind slabs are also expected on leeward slopes and may result in larger avalanches.
The new snow will require several days to settle and stabilize where it overlies a weak layer.>Use extra caution in lee areas in the alpine. Recent wind loading has created wind slabs.>Assess start zones carefully and use safe travel techniques.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The October rain crust and the early November surface hoar have been dormant for several days but have the potential to reactivate with the weight of the new snow. Smaller storm avalanches may have the potential to step down to one of these layers.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Caution around convexities and large, unsupported slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 2nd, 2013 2:00PM

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