Avalanche Forecast

Issued: Dec 28th, 2016 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Another pulse of snow and continued moderate to strong winds for Thursday. We have tricky conditions at treeline and above, and users should be very conservative with terrain choices. SH

Summary

Weather Forecast

Another pulse of snow starting mid day Thursday will see 10-15cm of snow and continued strong westerly winds. A NW flow with decreased winds will start Friday AM. Drier conditions for Friday and Saturday. Alpine temperatures will be in the -12 to -15 C range and will cool off Saturday night.

Snowpack Summary

Strong winds and light snow accumulations have formed fresh wind slabs 20-40cm thick in alpine lees. These sit over previous slabs up to 60cm thick at treeline and above. These slabs all 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

Visibility and observations were limited today, but still some reports of whumpfing and cracking and small fresh wind slabs (size 1 to 1.5) being easily skier triggered by avalanche control at the ski hills.

Confidence

Due to the number and quality of field observations

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. This weak, faceted layer will persist for some time.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Fresh wind slabs 20-40 cm thick have formed in the lees of alpine features. These will be touchy in the short term with the current snow and wind forecast. Once initiated, they may trigger a persistent slab on the Dec.19th facets.

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

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 29th, 2016 4:00PM