Avalanche Forecast

Issued: Dec 19th, 2012 4:07PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Increased winds are creating thin new slabs in the alpine and at treeline. If the forecasted winds arrive, the hazard will rise. Otherwise, great skiing on a generally stable snowpack.

Summary

Weather Forecast

Moderate confidence in the forecasted snowfall amounts.Thurs: Alpine temps -10/-15. 5-10 cms snow with higher values N of Lake Louise.Â Alpine winds moderate to strong from the SW.Fri: Alpine temps -10/-15. Clear. Alpine winds light from the S.Sat: Alpine temps -15/-20. 5 cms of new snow. Alpine winds light from the E.

Snowpack Summary

5-15 cms of new snow overlies a well settled midpack. At ridgetop elevations, moderate S/SW winds are forming thin soft slabs in the immediate lee on N through E. 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 Sunshine ski hill backcountry.

Confidence

Wind speed and direction is uncertain on Thursday

Problems

Wind Slabs

5-15 cms of new snow along with mod. S/SW winds is creating thin slabs in immediate lees at ridgetop elevations. In most areas, these slabs aren't thick enough to be a concern yet; however, forecasted mod. winds on thursday might elevate the hazard.

Be careful with wind loaded pockets while approaching and climbing ice routes.Stay off recent wind loaded areas until the slope has had a chance to stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

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.Avoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Dec 20th, 2012 4:00PM