Avalanche Forecast

Issued: Dec 17th, 2014 7:30AM

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

Avalanche Canada rbuhler, Avalanche Canada

A deeply buried weak layer remains a concern, especially on steep north facing slopes in the alpine. Remote triggering of this layer may still be possible.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The first of two weekend weather systems is expected to reach the interior on Friday. Thursday may see light scattered flurries and freezing levels should be around 1000m with light to moderate alpine winds from the SW. The Purcells region can expect 3-6mm on Friday with freezing levels around 1000m and moderate alpine winds from the SW. On Saturday freezing levels will rise to around 1500m and alpine winds are expected to be moderate from the west. Light scattered precipitation is expected on Saturday. The models currently have the second storm system reaching the interior early Sunday.

Avalanche Summary

No new avalanches have been reported since Monday. On Monday, explosive control produced a size 3 deep slab avalanche and a snowmobile triggered a size 1.5 wind slab. On Sunday, a report of a skier remotely triggering a size 2.5 avalanche from 5 meters away in the Dogtooth range alpine. This occurred at around 2300m in the alpine. Also reported was an explosive triggered size 2 persistent slab releasing around 60cm deep.

Snowpack Summary

A surface crust exists up to around 2200 m. Above this elevation is dry storm snow which is settling out and faceting. A new layer of large surface hoar is currently forming on the snow surface. In exposed alpine terrain, strong southerly winds last week may have resulted in variable distribution of the surface snow and the formation of wind slabs. The early November crust/facet layer is down around 1 m. Tests are suggesting that this layer is getting difficult to trigger but still has the potential to produce large avalanches. We received reports that this deep weak layer has resulted in remotely triggered avalanches over the weekend.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The likelihood of triggering a deep persistent slab has decreased but the consequences remain very high. Be wary of any slopes that did not release during the storms. Heavy triggers such cornice falls may be able to trigger a deep weak layer.
Remote triggering is a concern, watch out for adjacent slopes.>Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 18th, 2014 2:00PM

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