Avalanche Forecast

Issued: Dec 18th, 2012 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Good skiing can be found in sheltered locations. Remember, a stable snowpack in December is different than a stable snowpack in April. Many thin/ weak spots still exist in alpine features. Hopefully the forecast of 5-10 cms on Thurs comes true!

Summary

Weather Forecast

Wed: Alpine temps in the -10 / -15 range. 1-2 cms snow, up to 5 cm N of Lake Louise overnight. Winds moderate from the W. Thurs: Alpine temps -10/-15. 5-10cms new snow with higher values N of Lake Louise. Winds light from S/ SW. Fri: Arctic air moves in.Â Alpine temps -15/-20. Clearing skies. Winds light from SW.

Snowpack Summary

A few cm's of new snow overlies a slowly facetting snowpack. In the alpine, old windslabs exist and are visible as 'rippled' snow on the surface. These may be reactive to human triggering. The Nov. 6th crust is facetting out, and is now more of a facet layer than a crust in many places. This layer is giving hard to no results in compression tests.

Avalanche Summary

No new avalanches observed today by forecasters during a field trip in the Lake Louise ski hill backcountry.

Confidence

Forecast snowfall amounts are uncertain on Thursday

Problems

Wind Slabs

New snow is hiding old windslabs in lee terrain at and above treeline that may be sensitive to skier triggering. In the right terrain these could take the skier into a terrain trap.

Be cautious as you transition into wind affected terrain.The recent snow may now be hiding windslabs that were easily visible before the snow fell.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

We are seeing weakening of the Nov 6 crust in thinner areas due to facetting. Although we haven't seen activity on this layer recently, it is still the prominent feature in this years snow pack, and should be evaluated in bigger features.

Carefully evaluate and use caution around thin snowpack areas.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Dec 19th, 2012 4:00PM