Avalanche Forecast

Issued: Jan 1st, 2014 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, Wind Slabs and Storm Slabs.

snow safety, Parks Canada

Banff Yoho Kootenay.

The hazard may go to high Thursday if we get more snow than forecast. Given the sensitive nature of the basal weakness, it will be best to limit your exposure to avalanche terrain until we see what this storm produces. SH

Summary

Weather Forecast

Snowfall amounts have backed off from previous forecasts. Starting Thursday afternoon, we can still expect 10-20 cm of snow by Friday (lesser amounts in Eastern regions). Winds Thursday will be mod-strong westerlies, with gusts into the extreme range. This may bump the hazard to High in the bulletin region on Thursday and Friday.

Snowpack Summary

W. of the divide there is 40-70 cm of fresh snow over the past 6 days and 10-20 cm on the East. Continued west winds have added to the slab condition in the alpine and at treeline. The treeline snowpack depth is roughly 1 metre deep. The midpack is supportive on skis but is consists mostly of weak facets with a persistent weak layer at the ground.

Avalanche Summary

Avalanches to size 2.5 over the past few days have been reported with mainly the same characteristics, which are wind slabs failing to ground on the basal weaknesses. Two cornice triggered size 2 avalanches were observed on E/SE. facing Healy creek paths. These were new wind slabs which did not step down to ground and were roughly 40-50cm thick.

Confidence

Forecast snowfall amounts are uncertain on Thursday

Problems

Deep Persistent Slabs

This is the predominant layer in the snowpack, and full depth avalanches to ground have been observed daily over the past week. This will increase in frequency with the new snow.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

Watch for areas of wind loading. If a wind slab is triggered it may step down to deeper layers.

Be careful with wind loaded pockets while approaching and climbing ice routes.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Storm Slabs

This is mainly a problem at treeline and below, West of the divide where 40-70cm of snow has fallen over the last six days. There has been less wind in these areas, and high humidity has promoted slab development over the facets.

Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 2nd, 2014 4:00PM