Avalanche Forecast

Issued: Dec 11th, 2012 4:00PM

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

A.L. Horton, Parks Canada

Jasper.

Touchy wind slabs are found on a wide range of aspects. Stick to sheltered tree line slopes or glades for the best turns.

Summary

Weather Forecast

Moderate NW winds will ease through Wednesday to light from the SW by the afternoon. A few cm of snow are possible overnight and through the day on Wednesday. Expect seasonal temperatures (Highs -8, Lows -15) and cloudy skies.

Snowpack Summary

Moderate to strong winds have continued, shifting from the NW to the SW. Wind slab can be found on most lee slopes extending from the Alpine well into tree line elevations. Expect variable wind loading patterns as directions vary with local terrain influences. Cornices are well developed.

Avalanche Summary

An avalanche cycle has occurred in the past 24-48 hrs. Slab avalanches to size 3 have occurred on E to W aspects at alpine and tree line elevations and have stepped down to the basal facet layer. Large cornice failure has triggered large avalanches on the basal facet layer as well. Winds will ease, however, expect touchy conditions to continue.

Confidence

Due to the number and quality of field observations

Problems

Wind Slabs

Wind slab is present on all open lee slopes from the alpine into tree line elevations. Several natural slab avalanches have been observed on this layer today. Watch for reverse loading patterns and increasing natural activity.

Be careful with wind loaded pockets while approaching and climbing ice routes.Avoid freshly wind loaded features.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Deep Persistent Slabs

Slab avalanches and large cornice failures have triggered this weakness on E to W aspects in the alpine. Shallow snowpack areas and along the edges of snow pockets will be likely trigger spots.

Do not travel on slopes that are exposed to cornices overhead.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

A persistent facetted weakness can be found around a mid-pack crust.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 12th, 2012 4:00PM