Avalanche Forecast

Issued: Mar 20th, 2013 4:00PM

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

lisa paulson, Parks Canada

Banff Yoho Kootenay.

May see another 10-20 cm of snow tonight with the possibility of some reverse loading onto Southerly aspects towards the end of the storm. Keep to conservative route choices.

Summary

Weather Forecast

A system tonight could deliver another 10-20 cm with moderate west wind creating new wind slabs and adding to existing slabs. In some areas, this could be enough to overload existing weaknesses and another natural cycle may result. Winds will flip to moderate NW as the system passes and temperatures will cool. Skies will clear for the weekend.

Snowpack Summary

Over the past week, 60-80 cm of snow has fallen in the region with strong West winds. The storm snow is starting to bond to underlying layers West of the divide, but still may be of concern steeper features where the interface is a suncrust. East the divide, storm snow is a cohesive slab resting on a weak faceted snowpack.

Avalanche Summary

Yesterday a size 2.5 was noted in Redoubt bowl (near Lake Louise ski area) with a 400 m wide propagation with a crown 60-80 cm thick. Generally, natural activity has tapered, only a few naturals to size 2 were reported in the area yesterday in steeper alpine lee terrain. Skier triggering of recently developed slabs remains possible to likely.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

Expect new soft slabs to develop tonight and expect some reverse loading onto South aspects towards the end of the storm. Existing storm and wind slabs are 30-80 cm thick Tonight's storm will add stress to the underlying weaknesses.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

In shallow snowpack areas, especially East of the divide, the storm snow and wind slabs overlie a weak faceted mid-pack. Avalanches triggered in this region may steep down to ground.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Many large cornices loom overhead in the region. Be mindful of overhead hazards, especially during strong solar periods or during/after recent snowfalls and wind loading.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Mar 21st, 2013 4:00PM