Avalanche Forecast

Issued: Dec 17th, 2012 4:06PM

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.

Conditions are good for December. However, it is still early season and many of the bigger alpine features have not had a chance to fill in yet. Many thin spots still exist in the alpine leading us to have lower confidence in these features.

Summary

Weather Forecast

The drought continues... Temperatures are cooling off a bit (approaching -20 along the divide). We might see a couple cm's on monday night/ tuesday, and then a clearing trend for wednesday. ALP winds are forecast to increase to Moderate from the W tonight with the passing of a low pressure system and then ease again on Tuesday.

Snowpack Summary

A couple cm's of fluff overlies a well settled snowpack. In the ALP, 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 flight of the highway avalanche control paths as well as a team in the Lake O'hara area.

Confidence

Wind speed and direction is uncertain on Monday

Problems

Wind Slabs

There are some old windslabs on lee terrain at and above treeline that are 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

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 18th, 2012 4:00PM