Avalanche Forecast

Issued: Jan 19th, 2017 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

There is uncertainty around the deep persistent facets, how they will react to a user, and what will trigger them naturally. The best way to manage this uncertainty is through conservative terrain choices, and limiting exposure to overhead hazard. SH

Summary

Weather Forecast

A slow cooling trend over the next 3 days (-7 to -12C in the alpine) with dying SW winds.Â No major snow is in the forecast.Â

Snowpack Summary

10-30cm of new snow in the region(deeper amounts near the divide) with some wind slabs formed in lee terrain.Â The upper snowpack consists of wind layers of various thicknesses.Â The lower snowpack consists of facets and depth hoar, and below treeline the entire snowpack mainly consists of facets to ground.

Avalanche Summary

Many avalanches to size 2.5 have been reported in the last 24 hours. A size 1.5 skier accidental in the canyon on the approach to Bow Hut was reported yesterday with no involvement. A size 2 avalanche was reported from yesterday afternoon over the ice climb Cascade Falls, and explosive results at Lake Louise ski hill to size 2.5 to ground.

Confidence

Due to the number and quality of field observations on Thursday

Problems

Deep Persistent Slabs

The midpack in most areas is weak and facetted. Any slab sitting overtop of this weakness should be considered suspect and there is a high level of uncertainty around this layer.

Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Recent winds ranging from East to SW have created some new windslabs in alpine and treeline features. In some cases, these have been observed to provide enough weight to step down to the deep persistent layer, causing a larger avalanche.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 20th, 2017 4:00PM