Avalanche Forecast

Issued: Dec 22nd, 2016 8:00AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Wind Slabs and Loose Dry.

andrew jones, Parks Canada

Glacier.

Settling storm snow is sitting on a weak layer that is reactive to human triggers. Natural avalanche activity is dropping off, but careful decision making is essential.

Summary

Weather Forecast

Mainly cloudy today with isolated flurries and ridge winds gusting to 50km/h from the SW. Freezing level will rise to 900m with an alpine high of -8. Isolated flurries will continue until Saturday morning. For the holiday weekend, a high pressure ridge is expected to form bringing clear skies and cool temperatures until the next storm arrives.

Snowpack Summary

The recent storm snow has remained light and powdery for the past couple of days but we are starting to see settlement and the formation of a storm slab. Strong SW winds have formed wind slabs on lee features. The new slabs are poorly bonded to the December 18th interface of facets and surface hoar. All of this sits on a weak, facetted snowpack.

Avalanche Summary

Numerous natural avalanches were observed yesterday morning in the highway corridor ranging from size 2.5 to 3. On Tuesday a skier was partially buried by a skier accidental size 1 avalanche in the Asulkan drainage. It was 30-50cm deep and failed on the Dec 18th (see their MIN). They also remotely triggered a size 1.5 on a SW aspect.

Confidence

Due to the number of field observations

Problems

Storm Slabs

80cm of storm snow is settling into a slab. The storm snow is poorly bonded to a reactive layer of facets and spotty surface hoar.

Ski short pitches and regroup in safe spots.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Lots of light new snow and sustained SW winds will have loaded lee slopes forming stiffer slabs. Wind slabs are poorly bonded to facetted snow below. A field team confirmed that these slabs were touchy around ridges and in areas of cornice growth.

Avoid freshly wind loaded features.Watch for signs of instability such as whumpfing, or cracking.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Loose Dry

Where the new snow is unconsolidated heavy sloughing is expected. In steep terrain these slides could entrain enough mass to be an issue for skiers and riders.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be aware of party members below you that may be exposed to your sluffs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 23rd, 2016 8:00AM