Avalanche Forecast

Issued: Dec 15th, 2012 8:13AM

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

danyelle magnan, Parks Canada

Glacier.

Pay attention to alpine winds today. The stable conditions we have been enjoying may change rapidly due to SW winds loading lee slopes and forming new windslabs at and below ridgecrests.

Summary

Weather Forecast

A weak weather system will pass through the region today. Less than 5cm of new snow is expected, but winds will increase to moderate to strong from the SW. On Sunday, cool unsettled weather will continue with flurries and possible glimpses of sun. On Monday, a low pressure system will bring strong SW winds and ~10cm of new snow.

Snowpack Summary

Snowpack tests were conducted yesterday on N and SW aspects in the alpine. ~50cm of loose storm snow overlies a well settled snowpack. Tests found that the interface beneath the storm snow failed in with "easy to moderate" force but was resistant to move (RP). A surface hoar layer down 80cm and a crust down 1.5m would be hard to trigger.

Avalanche Summary

One new natural avalanche was observed along the highway. This size 2 loose avalanche was from a steep north facing alpine start zone affected by wind. Avalanche technicians traveling in the Illecillewaet and Asulkan drainages observed no new avalanches, nor did they experience any sluffing while skiing steep S and W slopes.

Confidence

Problems

Wind Slabs

Isolated pockets of windslab have been buried in the immediate lees of ridgecrests; likely in places where even a small avalanche would have high consequences. Winds will increase through the day and over the weekend and may form new windslabs.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

While the thick crust at the base of the snowpack has yet to be reactive, if it does produce an avalanche it will be very large. Cornice falls or other avalanches stepping down to this layer, or triggering from thin areas are possible.

Be aware of thin areas that may propogate to deeper instabilites.Choose the deepest and strongest snowpack areas on your run.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 16th, 2012 8:00AM