Avalanche Forecast

Issued: Feb 21st, 2016 7:58AM

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

matt.mueller, Alberta Parks

Kananaskis.

Complex snowpack means making simple terrain choices until these avalanche problems are given some time to resolve themselves. Cornices are massive at the moment and can easily trigger deeper instabilities causing large and destructive avalanches.

Summary

Confidence

High

Weather Forecast

Avalanche Summary

A small to medium cycle was observed today on the Spray Smith Dorrian Highway. Several large avalanches from size 2.5 to size 3 were observed on east through southeast aspects on and below large alpine faces and in some instances running close to the end (3/4 path) of their historical run-outs due to strong to moderate sustained winds yesterday and the week prior. Forecast temperatures and lighter winds will diminish natural avalanche activity.

Snowpack Summary

The snowpack in the alpine has approximately 5cms of low density fluff sitting over wind-pressed and buried wind slabs. On north aspects the bond between the older wind slab interfaces appears to have tightened up in the upper snowpack. The bond at the February 11th melt-freeze & sun-crusts interfaces on southerly aspects has not gained any strength. Recently built wind slabs will also be found at treeline and alpine ridge features on east through south aspects. The cornices high up on alpine ridge top features are immense. Lower elevations at treeline and below will be facetted and lacking structure as a result of shallow heights of snowpack.

Problems

Storm Slabs

South facing terrain with buried sun or melt-freeze crusts should be treated with great skepticism before committing to the line. Thorough investigation is a requirement if crusts are detected with a ski pole. Dig down and conduct a snowpack test.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid steep slopes below cornices.>Avoid steep Southerly aspects.>Avoid solar aspects.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Any steep terrain with wind slabs overlying sun crusts or melt freeze crusts should be avoided.

Dig down to find and test weak layers before committing to a line.>Caution in lee and cross-loaded terrain near ridge crests.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Persistent Slabs

Recent snowpack tests show sudden collapses on the Jan 6th facets and in other locations no results. Treat large scale alpine slopes with high caution and watch out for cornices that can trigger this layer especially shallow areas.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Avoid steep slopes below cornices.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

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