Avalanche Forecast

Issued: Feb 22nd, 2016 6:43PM

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

Conrad Janzen, Parks Canada

Banff Yoho Kootenay.

With the big high pressure system arriving it will be tempting to start looking at bigger lines. Remember that the structure of the snowpack is so poor that human triggering remains likely. Stick to conservative terrain for the next while.

Summary

Weather Forecast

A very strong ridge is moving into the region bringing clear skies and light NW winds on Tuesday. Temperatures will remain cool but the sun effect will be strong. This ridge is expected to remain in place for most of the week.

Snowpack Summary

Sun crusts at lower elevations. Recent wind slabs and cornice growth in the alpine with 30-50 cm of snow in the last week. A 50-100 cm slab overlies the January 6 persistent weak layer of surface hoar, facets and sun crust. Snowpack tests indicate an unstable bond on this layer. The lower snowpack is facetted and quite weak in thin snow pack areas.

Avalanche Summary

A lot of human triggered activity has occurred in the last three days ranging from size 1.5 to size 3! Monday a skier was caught and partially buried in a size 2 slab triggered near Richardson's Ridge at Lake Louise. Flights in the Lake Louise area on Sunday also showed an extensive natural avalanche cycle up to size 3 in the previous 48 hrs.

Confidence

Due to the number and quality of field observations

Problems

Persistent Slabs

50-100 cm of snow overlies the Jan 6th layer of surface hoar, facets and sun crust. Numerous avalanches have been triggered on this layer recently. In thin snow pack areas, many of these avalanches have stepped down to the ground.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid paths that have not avalanched recently.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Be aware of cross loaded features and the lees of ridges where recent moderate to strong W winds have formed wind slabs and developed fragile cornices. Recent wind slab avalanches have also stepped down to the persistent weak layer and the ground.

Use caution in lee areas. Recent wind loading has created wind slabs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Feb 23rd, 2016 4:00PM