Avalanche Forecast

Issued: Feb 20th, 2017 3:27PM

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

jeremy.mackenzie, Alberta Parks

Kananaskis.

A few very large natural avalanches have run to valley floor in the past 12hrs. Cautious route selection is advised, and be aware of overhead hazard.

Summary

Confidence

High -

Weather Forecast

Up to 5cm of new snow may fall tonight. Tuesday will be mainly cloudy with Alpine temperatures near -8 C. Winds will be light from the West. Another wave of precipitation is expected on Thursday.

Avalanche Summary

A few naturally triggered slab avalanches between size 2.5 and 3.0 have occurred in the past 12hrs. These slabs ranged between 30 and 70cm deep, occurred in steep Alpine terrain on East or South-East aspects, and ran to valley floor.

Snowpack Summary

15cm of new snow in the past 24hrs, brings recent storm snow totals to 20 to 25cm at Treeline. The storm snow has minimal wind effect below 2500m, and overlies a temperature crust on all aspects below 2100m, and up to 2300m on solar aspects. Moist snow on solar aspects by early in the afternoon. Snow profile at Treeline today confirms a dense midpack overlying a very weak base. Snowpack stability tests indicate a concerning failure within the basal weak layers. Although these results were in the 'hard' range, the possibility for a full depth avalanche is very real.

Problems

Wind Slabs

Wind slabs between up to 50cm thick have formed in lee and cross-loaded features in the Alpine and Treeline. A few naturally triggered wind slab avalanches have occurred in the past 12hrs. These slabs were very large and have run full path.

Avoid lee and cross-loaded terrain near ridge crests.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Persistent Slabs

A dense slab formed in late January is buried as much as 100cm in the snowpack. This slab is potentially still trigger-able, and could result in a very large avalanche

Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

Past avalanches have stepped down to this layer. Thin areas and transitional terrain remain a concern.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Feb 21st, 2017 2:00PM