Avalanche Forecast

Issued: Dec 15th, 2014 8:41AM

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

rbuhler, Avalanche Canada

Purcells.

A deeply buried weak layer is still producing large destructive avalanches in isolated areas and may be remotely triggered from a distance. Use extra caution around steep, unsupported alpine terrain.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

High pressure persists over the interior for the forecast period. A mix of sun and cloud is expected on Tuesday with treeline temperatures around -8 and light alpine winds. Wednesday and Thursday may see an increase in cloud cover while treeline temperatures should remain around -8 and alpine winds should remain light.

Avalanche Summary

On Monday, explosive control produced a size 3 deep slab avalanche.Â A report on Sunday 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 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.Â We received reports that this deep weak layer has resulted in remotely triggered avalanches over the weekend.

Problems

Persistent Slabs

The likelihood of triggering a persistent slab has decreased but the consequences remain very high. Be wary of any slopes that did not release during the storms. Remote triggering of this layer may also be possible.

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

Wind Slabs

Strong southerly winds last week created wind slabs in the alpine. Triggering these slabs has become more stubborn but they remain a concern, especially in steep, unsupported terrain.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 16th, 2014 2:00PM