Avalanche Forecast

Issued: Feb 18th, 2017 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

http://www.pc.gc.ca/apps/scond/Cond_E.asp?oID=26206&oPark=100092Natural activity has slowed with the cooling temperatures, but tricky and dangerous avalanche conditions exist. The potential to trigger large avalanches is very real.

Summary

Weather Forecast

Sunday looks to be mainly cloudy with a few cm possible and mainly light SW winds. Freezing levels to 1700m. Light snow in the forecast over the next few days with and continued light winds.

Snowpack Summary

40-60 cm of snow in the past week combined with moderate SW winds created windslabs on lee and crossloaded features. This rests on hard windslabs at treeline and above which overlie a structurally weak snow pack. Below 1900m a surface crust has formed from previous rain and warm temperatures, followed by subsequent cooling.

Avalanche Summary

A size 3 on the W face of Noseeum peak (Hwy 93 N) was reported to have run in the last 12 hours, stepping to ground. 2 large avalanches outside the Lake Louise and Sunshine ski area boundaries reported yesterday also stepped down to ground. Smaller wind slabs to size 1.5 in the alpine are still being triggered, although harder to initiate today.

Confidence

Due to the number of field observations on Saturday

Problems

Deep Persistent Slabs

There is a thick slab over a structurally weak snowpack at all elevations. Likely areas of triggering would be from thin parts of a slope at treeline and above which can propagate to deeper areas and cause a large avalanche.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Previous fresh snow and moderate SW winds have created windslabs which have been most reactive in alpine areas.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 19th, 2017 4:00PM