Avalanche Forecast

Issued: Mar 18th, 2017 3:00PM

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

jeremy.mackenzie, Alberta Parks

Kananaskis.

Avalanche control is planned for HWY 742 between 10:30 and 14:30. Expect delays.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Up to 20cm of new snow is possible over the next 12 hours, with rain at lower elevations until temperatures cool late this evening. Sunday will be a mix of sun and cloud with much cooler temperatures and westerly winds gusting to 65 km/h.

Avalanche Summary

Visibility was very limited today. An avalanche cycle continues, with recent slab avalanches up to size 3.5 occurring on all aspects at all elevations. All of the avalanches are stepping down to the basal weak layers. Crowns are up to 1.5m deep and propagations have been wide. Many avalanches have reached or exceeded their historic run-outs, in some cases destroying significant tracts of mature forest.

Snowpack Summary

Rain fell through the day up to an elevation of 2200m. The snowpack is isothermal at lower elevations. Wind slabs are present in Alpine and Treeline areas on all aspects but localized additional loading has been noted on lee features. Cornices are large and sagging. Extensive avalanche activity has occurred over the last few days, that has all stepped down to the basal weaknesses resulting in large destructive avalanches.

Problems

Storm Slabs

Warm temps, wind and new snow are the perfect mix for storm slab development. Expect to find these in lee and cross-loaded features in the Alpine and just into Treeline.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Wind Slabs

These still exist from previous storms and are buried under 30-40cm of newer snow. They will be especially hard to identify with the new snow, but are still quite triggerable.

Avoid steep lee and cross-loaded slopes

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Deep Persistent Slabs

Any avalanche initiated in the upper snowpack will likely step down to the basal layers resulting in a very large avalanche. New snow and wind will add a significant and rapid load to this layer. This is a scary layer with huge destructive power!

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Valid until: Mar 19th, 2017 2:00PM