Avalanche Forecast

Issued: Dec 13th, 2014 7:43AM

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

Avalanche Canada pgoddard, Avalanche Canada

Recent avalanches have failed on a deeply buried weak layer. Although the chances of triggering a deep slab are dropping, the consequences remain high.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Mainly clear cool weather is expected until late Monday, when a system is expected to brush up against the coast and bring light snowfall. Freezing levels are near 1000m. Light to moderate SE winds.

Avalanche Summary

A natural cycle up to size 3 was observed throughout the recent storm. These included wind slabs and storm slabs, primarily at alpine elevations; and loose wet and wet slab avalanches at treeline and below. Some of these events failed on a crust /facet layer buried in late November and were more than 1 metre deep. On Thursday night a slab failed naturally in terrain that had previously been controlled with explosives, 1.5-2 m deep, with good propagation on the crust/facet layer. A second 1.5m deep slab also failed naturally on the same layer on Friday. On Saturday, a vehicle remotely triggered yet another slab 1m deep, on a north-facing slope in the alpine. Check out some recent photos here: http://www.wayneflannavalancheblog.com/.

Snowpack Summary

The recent prolonged storm dropped 100-200mm of water, with fluctuating freezing levels bringing rain at times to alpine elevations. Snow also accumulated above treeline, leading to deep wind slabs. Now the storm is over, storm slabs and wind slabs may remain problematic for a day or two. However, my bigger concern is a buried crust/facet layer which formed in November and is now down 1-2 m. This woke up with the recent storm snow loading and has the potential for deep slabs and wide propagations, and does not inspire huge confidence. The likelihood of triggering this beast is dropping, however the consequences remain high.

Problems

Wind Slabs

An icon showing Wind Slabs
The recent storm has left behind slabs on lee slopes. A wind slab could fail on a deeply buried crust layer, creating a surprisingly large avalanche.
Avoid convexities or areas where the snowpack depth transitions from thin to thick.>Use caution in lee areas in the alpine. Recent wind loading has created wind slabs. Avoid these features by traveling on ridge tops or ribs.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 14th, 2014 2:00PM

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