Avalanche Forecast

Issued: Dec 18th, 2013 8:07AM

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

danyelle magnan, Parks Canada

Glacier.

The storm continued overnight, depositing more snow with strong winds. Good group management, minimizing exposure to overhead hazard, and conservative terrain selection are highly recommended.

Summary

Weather Forecast

As the storm exits the region we should get lingering flurries this morning, with moderate winds shifting to the NW as an arctic ridge of high pressure moves in. We may see some sunny breaks this afternoon, and Thursday looks sunny and cold with temps dropping to -20 overnight. Friday will be cloudy and snowing with strong SW winds at ridgetop.

Snowpack Summary

80cm of storm snow sits over a variety of surfaces from December 8th like surface hoar lower down, facets and variable wind slabs at higher elevations. Strong winds have formed windslabs and wind loaded pockets above treeline. Below this are 2 persistant weak layers and the snowpack is facetted. As the load increases these layers may wake up.

Avalanche Summary

A widespread natural avalanche cycle continues. Most were initiated in the alpine and at treeline, running well into runouts, but several triggered slabs below treeline. Along the highway, 1 size 3.5, 4 size 3 and 20 size 2 avalanches were observed yesterday. On Monday skiers reported large natural avalanches occurring up the Connaught drainage.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

This weeks storm deposited 80cm of snow under ideal slab forming conditions. This slab sits on a weaker surface that may be reactive to skiers and riders, and the slab is deep enough to produce large avalanches.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Wind Slabs

Strong winds throughout the storm, with lots of snow available for transport, have loaded lee slopes and formed windslabs at treeline and above.

Avoid freshly wind loaded features.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Persistent Slabs

Buried surface hoar down between 80 to 110cm with a recent significant snow load should remain a concern for rider triggering. These layers may also be triggered by other avalanches, producing very large avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 4

Valid until: Dec 19th, 2013 8:00AM