Avalanche Forecast

Issued: Nov 20th, 2012 4:31PM

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

brian webster, Parks Canada

Banff Yoho Kootenay.

Summary

Weather Forecast

The storm is over. Expect mixed sun and cloud with light snow accumulations through the end of the week. Temperatures will cool off slightly with freezing levels near valley bottom. Winds forecast to be light from the west.

Snowpack Summary

30 cm of storm snow at tree-line along the continental divide along with moderate to strong westerly winds has created wind-slabs in the alpine. Wind slabs are reactive to skier triggering on steep lee terrain. Easy shears at storm snow interface and mod shears down 60 cm on Nov 6 crust.

Avalanche Summary

Sunshine Ski Hill reported several class 1 avalanches ski cut within storm snow on steep rolls. During field trip to Bow Summit area no natural avalanches were observed although visibility was not great. Some whoomphing was heard at treeline.

Confidence

Problems

Wind Slabs

30 cm HSt and westerly winds producing wind slabs on lee aspects down into treeline elevations. Wind slabs are touchy and are reactive to skier triggering.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

Although no recent natural avalanches has been observed on this layer, this still is a significant interface to be aware of. Latest storm inputs may make this layer close to being overloaded. Easy to mod shears found on this layer at Bow Summit .

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Nov 21st, 2012 4:00PM