Avalanche Forecast

Issued: Nov 29th, 2014 7:55AM

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.

pgoddard, Avalanche Canada

South Rockies.

A Special Public Avalanche Warning is in effect. Take a conservative approach this weekend. Don't go nuts just because there is fresh snow!

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Sunday/Monday/ Tuesday: Very cold and dry. Mainly light to moderate winds, increasing to strong south-westerly for a time on Monday.

Avalanche Summary

Explosives triggered two very large (size 2.5 and 3.5) slabs in the south of the region on Thursday around treeline. These failed on a weak layer of facets buried about a week ago. We haven't had any newer reports, but I'd expect some further avalanche activity to occur this weekend in response to the recent snow and wind, with the chance of triggering a deeper weakness and creating a very large event.

Snowpack Summary

As we begin our forecasting season, we are working with very limited field data. If you have been out in the mountains, we'd love to hear from you. Please email us at forecaster@avalanche.ca.Half a metre or so of new snow is likely to have been redistributed by wind into fresh slabs on lee slopes. Natural avalanches spilling down steep headwalls may continue for a day or two. A weak layer (of facets over a crust) which formed during November's dry spell is now buried a metre or more down. Avalanches failing on this layer have the potential to propagate widely, leading to very large events. It's a good weekend to be cautious: avoid grouping up in avalanche terrain and stick to low angle slopes.

Problems

Storm Slabs

Recent storm snow will take some time to stabilise. Winds may have caused the formation of slabs on lee (downwind) slopes. Storm snow may spill down steep head walls and overload slopes below.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of sluffing in steep terrain.>Be cautious as you transition into wind affected terrain.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A touchy weak layer is now buried a metre or so down in the snowpack. It may be reactive to the weight of new snow, wind-loading or the additional weight of a skier or sledder. Avalanches on this layer could be surprisingly large.

Avoid convexities or areas with a thin or variable snowpack.>Avoid freshly wind loaded features.>Choose regroup spots that are out of avalanche terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Nov 30th, 2014 2:00PM