Avalanche Forecast

Issued: Nov 21st, 2012 4:49PM

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

brian webster, Parks Canada

Banff Yoho Kootenay.

Summary

Weather Forecast

Heavy snow fall warning for Banff and Lake Louise tonight. Some forecasts say 10-15 at valley bottom locations. Can expect double this amount in the alpine. Temperatures will get colder towards the end of the week.

Snowpack Summary

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

Avalanche Summary

Â No natural avalanches were observed throughout the forecast area today. Several naturals were reported yesterday from the Icefields Parkway. Sunshine Ski Hill reported up to Class 2.5 slabs with explosives running in the storm snow.

Confidence

Intensity of incoming weather systems is uncertain on Wednesday

Problems

Storm Slabs

Heavy snowfall forecasted for night of Nov 21. Expect 10-15 cm at valley bottom with double that amount in the alpine. This new snow will increase the avalanche hazard for Thursday.

The new snow will requires several days to settle and stabilize.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

Recent new snow and winds have produced wind slabs on lee aspects in the alpine. These slabs are reactive to skier triggering in specific locations.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

Although no recent natural avalanches have been observed on this layer, this still is a significant interface to be aware of. Latest storm inputs may be enough to overload this layer.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Nov 22nd, 2012 4:00PM