Avalanche Forecast

Issued: Nov 22nd, 2017 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Persistent Slabs, Wind Slabs and Loose Wet.

snow safety, Parks Canada

Banff Yoho Kootenay.

The first major avalanche cycle of the season will peak on Thurs. Avoid all avalanche terrain. There is a significant weak layer deep in the snowpack that is active and we expect widespread avalanche activity.

Summary

Weather Forecast

A strong south-westerly flow dominates the region bringing rain, snow and warm temperatures. Rain is expected to reach 2200m Thursday morning followed by snow as the moist air lifts over the colder incoming air. Thursday evening should be winter again with colder temps and snow..

Snowpack Summary

The snowpack near treeline has a variable depth between 60cm and 1m. The main feature of concern is a facet layer associated with the halloween raincrust. This layer has been causing avalanches, extensive whumphing, and has had good propagations.

Avalanche Summary

Visibility was generally poor throughout the forecast area but some slab avalanches to size 2.0 were noted throughout.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Persistent Slabs

This is an active avalanche problem and is the main reason people should avoid all avalanche terrain Thursday. The problem exists in most terrain and will become overloaded with the incoming storm. Watch overhead hazard.

Avoid all avalanche terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Winds up to 100 km/hr are forecast for Thurs which will load the new snow onto leeward aspects. Windslabs should be expected near all ridges and gully areas and can be expected to become large once triggered.

Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

Warming temperatures and rainfall will create wet avalanches in gully areas below treeline. Ice climbers in particular should avoid gully climbs for the next 48-hours.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Nov 23rd, 2017 4:00PM