Avalanche Forecast

Issued: Nov 29th, 2013 8:56AM

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

jlammers, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

Saturday: Light to moderate snowfall with moderate westerly ridgetop winds. Freezing level around 1400 m.Sunday: Moderate to locally heavy snowfall with strong westerly winds. Freezing level around 1400m.Monday: Light to moderate snowfall with light southwest winds. Freezing level dropping to 1000m

Avalanche Summary

No recent avalanche activity has been reported.

Snowpack Summary

Snowpack depths at treeline are approximately 70-100cm. On the surface light amounts of new snow override a variety of old surfaces which include: old wind slabs, melt-freeze crusts and surface hoar.Probably the most important layer we've heard about in this region is a crust near the base of the snowpack that has sugary facets associated with it. In mid November, several large avalanches were reported on this weakness. A recent snowpack test in the backcountry near Kicking Horse on a NW aspect gave moderate but "sudden" results, indicating this layer is likely still triggerable. While this layer is probably slowly gaining strength, it may 'wake-up' with the new snow load forecast for the weekend. The most likely place you'd trigger this layer is on smooth, planar, north facing slopes, especially if the snowpack is unusually shallow in that area.

Problems

Persistent Slabs

The most destructive layer is a crust with sugary facets that lies 5-40 cm off the ground. The most likely place to trigger it would be on a smooth, planar slope on a northerly aspect in a shallow snowpack area.

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.>Be aware of the potential for large, deep avalanches due to the presence of a buried crust/ facet combo.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Storm Slabs

Ongoing snowfall will add to a developing storm slab problem. Watch for increased triggering in wind-affected terrain.

The new snow may require several days to settle and stabilize due to the presence of newly buried weak layers.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Nov 30th, 2013 2:00PM