Avalanche Forecast

Issued: Mar 21st, 2016 8:22AM

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

jeremy.mackenzie, Alberta Parks

Kananaskis.

A fatal avalanche occurred yesterday in a cross-loaded terrain feature (see avalanche discussion for further details). Cautious route-finding is essential in this period of continued CONSIDERABLE hazard.

Summary

Confidence

High

Weather Forecast

Tuesday will be a mix of sun and cloud with alpine temperatures reaching a high of -2 C. Freezing levels will reach 2000 metres. Ridge-top winds will be from the northwest at 10-25 km/h. Wednesday, Thursday and Friday will bring light accumulations of new snow, cool temperatures and strong west winds.

Avalanche Summary

Several large avalanches have occurred over the past week. Many of these have been triggered by cornice failures, and most have failed on the Jan 6th layer and/or ground.A fatal avalanche occurred on Tent Ridge on Sunday March 20, 2016. A solo snowshoer triggered a size 3.0 on a North aspect and was completely buried. The avalanche initiated near 2400m and ran for over 800m. The fracture ranged from 40 to 150cm deep and involved a wind slab that stepped down to the Jan 6th layer and to ground. The subject who was not wearing a transceiver was recovered by rescue crews on Monday morning.

Snowpack Summary

A few cm's of new snow has fallen in the past 24hrs. This overlies a variety of previous surfaces including wind slab and facets on N and E aspects, and crusts on all solar aspects. There are numerous buried crusts on solar aspects that are giving widely variable results in snowpack tests. Recently formed wind slabs are found primarily in the Alpine in lee and cross-loaded features, and there are a few Treeline features were this condition can be found. These slabs range from 30 to 60cm thick. The persistent weak layer from Jan 6th buried up to 100cm in the snowpack has been active in the past week responsible for several large natural avalanches and one fatal human-triggered avalanche (see avalanche discussion). Cornices have also been failing in the past week, also producing large avalanches on the underlying slopes.

Problems

Persistent Slabs

Wind slabs up to 40cm thick are present in lee and cross-loaded features in alpine areas and in very specific locations at treeline.

Avoid lee and cross-loaded terrain near ridge crests.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Cornices

Cornices are large and we have seen a few recent collapses with the warmer temperatures and continued loading. When these do fail the heavy loads on underlying slopes may awaken the basal instabilities and produce very large avalanches.

Pay attention to overhead hazards like cornices.>Stay well back from cornices.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 6

Deep Persistent Slabs

Basal facets and the Jan 6th interface are likely to be triggered from thinner snowpack areas. Recent avalanche activity has also stepped down to this layer producing very large avalanches.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Mar 22nd, 2016 2:00PM