Avalanche Forecast

Issued: Jan 21st, 2019 4:00PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

While natural avalanche activity has tapered off, human triggering of large slab avalanches on the deep persistent layer is still a strong possibility. Remain conservative with your terrain choices, especially in thinner snowpack areas.

Summary

Weather Forecast

Temperatures will increase slightly on Tuesday but remain near -10 C at treeline. Winds will pick up out of the SW on Tuesday morning, becoming strong by late afternoon. A few cm's of snow is expected but accumulations will be limited. On Wednesday winds are expected to calm down, with 5-10 cm snow arriving before a clearing trend begins Thursday.

Snowpack Summary

5-15 cm of snow sits over the Jan 17 layer of surface hoar, or sun crust. Thin wind slabs can be found in alpine lee areas from strong SW winds on Saturday. Of greatest concern are the weak facets and depth hoar at the base of the snowpack. In thinner snowpack areas with less than 150 cm of snow, triggering a slab on these facets is more likely.

Avalanche Summary

Little natural avalanche activity has been observed over the last week. A group in the Emerald Lake area triggered a wind slab on Saturday in lee alpine terrain, and a group on Dolomite Shoulder triggered a slab on the basal facets on Sunday. Small wind slabs have been triggered by control work at the local ski hills in the last few days.

Confidence

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

Problems

Deep Persistent Slabs

Weak facets and depth hoar at the base of the snowpack have a significant slab (50-130cm thick) sitting above them. While natural avalanche activity has decreased, human triggering of this layer is still possible, especially in thin snowpack areas.

Be aware of the potential for wide propagations which could result in large avalanches.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Wind Slabs

Southwest winds in the moderate to strong range on Saturday created thin, soft wind slabs in the alpine 10 to 20 cm deep. Use caution in lee areas.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Jan 22nd, 2019 4:00PM