Avalanche Forecast

Issued: Dec 6th, 2014 4:30PM

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

Conrad Janzen, Parks Canada

Banff Yoho Kootenay.

Warmer temperatures and moderate W winds will help create more of a slab over the weak base in our snowpack. Human triggered avalanches remain possible especially in areas with recent wind effect.

Summary

Weather Forecast

Mild temperatures, moderate W winds and a few flurries are forecast for tonight with a bit of a clearing trend on Sunday and Monday. Tuesday we may see a few more flurries but accumulations are expected to be minimal.

Snowpack Summary

Warmer temperatures today are promoting settlement of the upper snowpack and creating more of a slab over the basal facets especially in wind affected areas. The lower half of the snowpack is poorly structured, with facets (Nov 24th) below the recent storm snow, thin crusts (Nov 6th) below this, and then depth hoar near the ground.

Avalanche Summary

Little natural activity has been observed recently however explosive triggered slab avalanches up to size 2.5 were reported yesterday from the ski areas with the slab failing on the basal facets and crusts near the ground. These kinds avalanches would result in a dirty, rough ride through scree, rocks and trees and human triggering is possible.

Confidence

Due to the number of field observations

Problems

Deep Persistent Slabs

The primary problem in the snowpack is the interface between the recent storm snow and the November 6th and 24th facet/crust interfaces. This is the problem responsible for the majority of the avalanches in the past week. Watch for remote triggering.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Mild temperatures and moderate W winds will cause wind slabs to develop in exposed areas at tree line and above. Watch for pockets of hard slab near ridge tops and on cross loaded features.

Watch for whumpfing, hollow sounds, and shooting cracks.Be careful with wind loaded pockets while approaching and climbing ice routes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 2

Valid until: Dec 7th, 2014 4:00PM