Avalanche Forecast

Issued: Nov 20th, 2012 8:05AM

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

danyelle magnan, Parks Canada

Glacier.

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Summary

Weather Forecast

Continued southwesterly flow will bring mild temps, moderate to heavy precipiation, and moderate to strong southwesterly winds. The system is tracking slightly south of Rogers Pass; areas south of the highway will likely get more new snow.

Snowpack Summary

24cm of snow is adding to the load on the Nov 6 crust, down 60-80cm. It appears to be more reactive in the Asulkan Drainage where tests are easy sudden planar. A cohesive storm slab has formed and is reactive where is overlies the Nov 16 sun crust down 40.

Avalanche Summary

Recent avalanche activity has been linked to spikes in wind speeds at ridgetop, loading lee slopes. This mornings avalanche patrol observed 6 size 3 and 4 size 2.5 slab avalanches from steep north and south facing slopes, running into fans.

Confidence

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

Problems

Storm Slabs

The storm slab is building and becoming more cohesive with mild temperatures and high humidity. Reports of shooting cracks and planar test results up the Asulkan indicate that it may fail on the right piece of terrain- a convex or unsupported slope.

Choose well supported terrain without convexities.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Moderate to strong S-SW winds are transporting the available storm snow, forming windslabs on exposed lee slopes. Recently large avalanches have been occurring when winds increase, overloading lee slopes.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Be cautious as you transition into wind affected terrain.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Nov 21st, 2012 8:00AM