Avalanche Forecast

Issued: Dec 27th, 2016 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Some light snow and strong winds are keeping the sensitivity of the Dec.19th facet interface elevated. Reports of whumpfing, cracking and natural avalanches over the last 12 hours. Its a tricky time for assessing this problem. SH

Summary

Weather Forecast

Continued strong Westerly winds Wednesday and light snow.Â Thursday another pulse of snow (10cm) along the divide.Â Alpine temperatures will stay in the -12 to -15C range and will cool off Friday as a NW flow begins to take over.

Snowpack Summary

Strong winds and light snow accumulations have formed thin wind slabs 10-20cm thick in alpine lees. These sit over previous slabs up to 60cm thick at treeline and above. These wind slabs sit over the poorly bonded Dec.19 facets. The Nov crust is 30-80cm deep. While it is not currently producing avalanches, we expect it could with more snow load.

Avalanche Summary

Numerous size 1.5 - 2 avalanches were observed between Bow Summit and Lake Louise on peaks such as Observation, Crowfoot and Dolomite. These slides appeared to be 24 hours old. As well, 2 naturals were observed off of the N. side of Mt. Fairview today. They were likely initiated by wind transport but the failure layer is unknown.

Confidence

Due to the number and quality of field observations on Tuesday

Problems

Persistent Slabs

Wind slabs up to 60cm+ from last week sit on top of a weak layer of facets (Dec 19 layer). This interface is poorly bonded, resulting in many recent avalanches. Some fresh snow overnight and strong winds are adding to this problem.

Be aware of the potential for wide propagations due to the presence of hard windslabs.Be careful with wind loaded pockets while approaching and climbing ice routes.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 28th, 2016 4:00PM