Avalanche Forecast

Issued: Dec 1st, 2012 8:01AM

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

danyelle magnan, Parks Canada

Glacier.

Summary

Weather Forecast

A very mild and moist SW'ly flow pattern will continue. Precipitation will continue through the weekend, bringing another 5-10 cm today, 5cm Sunday, and 10-15 on Monday. Freezing levels are presently at 1300m and may rise to 1500m before dropping to 800m overnight. Winds will be transporting snow; moderate to strong from the SW.

Snowpack Summary

Up to 20 cm of wet, dense snow is forming a storm slab sitting on a suncrust of steep solar slopes and surface hoar elsewhere. The surface hoar layer was largest at treeline, and were mixed with large stellar crystals. The Nov 6 crust is facetting and in recent tests it takes a hard force but gives sudden planar or sudden collapse results.

Avalanche Summary

4 natural size 2 avalanches were obersved adjacent to the highway yesterday. They were on N aspects, starting at eleveations of 22-2800 m, and ran into the avalanche fans. Cheops N4 (aka STS couloir) ran naturally on Thursday into the avalanche fan.

Confidence

Problems

Storm Slabs

20 cm of heavy storm snow has buried a layer of surface hoar, and on southerly aspects a sun crust. With forecast snow and wind over the weekend, this layer will become a concern. It will be easy to trigger and as the slab develops it may propagate.

Choose well supported terrain without convexities.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

The Nov 6 crust complex has yet to wake up. While the likelihood of triggering is low, it will produce large avalanches. As the load on this layer increases, it may become reactive. Smaller avalanches may step down to this deeper layer.

Space out and travel quickly through runout zones of avalanche paths.Minimize exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 2nd, 2012 8:00AM