Avalanche Forecast

Issued: Apr 21st, 2014 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Loose Wet, Deep Persistent Slabs and Cornices.

ian jackson, Parks Canada

Banff Yoho Kootenay.

High freezing levels and rain will raise the avalanche danger and make for poor travel conditions at lower elevations. We have low confidence in the accuracy of the weather forecast, so pay attention to temps/ precip at the local level.

Summary

Weather Forecast

Tues: High freezing levels (2400m in the north and west - 2700m in the south and east) and 5-10 mm of precipitation. Moderate south winds at ridgetop. Precip amounts may vary locally Wed and Thurs: Cooling with freezing levels dropping to 1000 - 1600m, light precipitation and winds switching to moderate from the west.

Snowpack Summary

10-30 cm's of recent new snow with moderate W winds has formed some soft slabs at ridgetop on N-E aspects. Warm temps are causing these to settle out quickly. Temperature crusts exist to 2200m on polar aspects and higher on solar aspects. The midpack is generally strong, however the basal facets persist especially in thin snowpack areas.

Avalanche Summary

Some pinwheeling and wet loose avalanches to size 1 out of steep solar, otherwise, no new avalanches were observed or reported today.Â

Confidence

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

Problems

Loose Wet

A weak freeze overnight combined with rising freezing levels and rain will further saturate and destabilize the snowpack at all but the highest elevations.

Avoid avalanche terrain during periods of rain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

The warm temps may reawaken the basal layer in some areas. Wait until things cool down before exposing yourself to big terrain.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Avoid areas with overhead hazard.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Cornices

Warm temps and rain will destabilize cornices and make them more likely to fall off. A cornice failure could be a large enough trigger to wake up a deep persistent slab.

Do not travel on slopes that are exposed to cornices overhead.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 22nd, 2014 4:00PM