Avalanche Forecast

Issued: Feb 2nd, 2013 4:00PM

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

chris gooliaff, Parks Canada

Banff Yoho Kootenay.

Strong winds later in the day on Sunday, along with light snow, may cause local instabilities in lee features tomorrow and Monday.

Summary

Weather Forecast

Temperatures should drop a few degrees on Sunday, with increasing cloudiness and light snow (2-4cm) in the evening. Strong winds will pick up from the W/NW late in the day. Monday shows temp's continuing to drop slightly, with no snow and moderate winds.

Snowpack Summary

Two main layers in the upper pack are Jan 23 and Jan 6 surface hoar/ facets or suncrust down 25 & 55. Watch for wind slabs in all open areas. These may be easily triggered from thin snowpack areas in steep terrain.

Avalanche Summary

Recent cornice fall triggered several large slides to size 3 on southerly aspects on Mt Bosworth and Mt Field. Avalanche control today produced several slides to size 2-2.5 on Mt Bosworth. A size 2 skier-triggered avalanche near Katherine Lake (Dolomite Circuit area) was reported from yesterday.

Confidence

Problems

Wind Slabs

Isolated wind slabs in steep terrain features may be human triggered in thin, weak areas or run naturally with additional loading (cornices). Several recent cornice falls indicate it is time to start watching the big, fat snow-rolls at ridge top.

Avoid steep slopes below cornices.Be aware of thin areas that may propogate to deeper instabilites.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

In Kootenay and Yoho there is a buried surface hoar and/or crust layer down about 50cm. Though little activity has been observed on this layer, it is still producing sudden planar results in tests and should be monitored.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Feb 3rd, 2013 4:00PM