Avalanche Forecast

Issued: Dec 9th, 2014 4:20PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Warm temperatures and rain will destabilize the already weak snowpack especially at lower elevations. Ice climbers in particular should stay out of low elevation gullies.

Summary

Weather Forecast

Strong southwesterly winds, light precipitation, and warm temperatures with freezing levels to 2000m will dominate on Wednesday and Thursday. Temperatures will drop and winds will ease on Friday.

Snowpack Summary

Warmer daytime temperatures are promoting settlement of the upper snowpack and creating more of a slab over the basal facets/ rain crust 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

Avalanche control work today at the Lake Louise Ski area triggered avalanches to size 2 in terrain that had been previously controlled. This demonstrates that the weak layers at the base of the snowpack were not cleaned out in last weeks avalanche cycle and will likely be with us for some time.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Thursday

Problems

Deep Persistent Slabs

The primary problems in the snowpack are the Nov. 6th and 24th facet/crust interfaces. These layers are most reactive in alpine/ treeline areas where the wind has slabbed up the surface snow.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Loose Wet

Warm temperatures and rain will increase avalanche activity especially at lower elevations and in gully features.

Choose ice climbs that are not exposed to avalanches from above.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 10th, 2014 4:00PM