Avalanche Forecast

Issued: Jan 20th, 2019 4:02PM

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.

tim haggarty, Parks Canada

Banff Yoho Kootenay.

While natural activity has dropped off, human triggering of a large slab avalanche on the deep persistent layer is a strong possibility. Remain conservative with terrain selection especially in thin snowpack areas.

Summary

Weather Forecast

Temperatures will continue to cool through to Tuesday morning to -10C to -15C values at treeline. A weak system will bring modest amounts of snow beginning Monday night with winds increasing to strong in the alpine Tuesday as temperatures climb back to -5 to -10 values at treeline. Cloud and light snow is forecast to continue through Thursday.

Snowpack Summary

5 to 15 cm of recent snow buried suncrusts and some surface hoar. Moderate to Strong SW winds created small soft winslabs in the alpine Friday and Saturday. Of greatest concern are the weak facets and depth hoar in the lower half of the snowpack. In thin snowpack areas (150cm or less) triggering a slab over this layer is more likely.

Avalanche Summary

Very little natural activity has been observed over that last week. A party in the Emerald Lake area triggered a slab during Saturday's storm in lee alpine terrain. Avalanche Control workers at the ski hills have been working with small soft windslabs for the last two days. We have entered a low likelihood, high consequence period for avalanches.

Confidence

Problems

Deep Persistent Slabs

Weak facets and depth hoar are found just above the ground have an significant 50-140cm thick slab sitting above them. While natural activity has dropped off, human triggering is still possible. Be very cautious with 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 deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Wind Slabs

Southwest winds in the moderate to strong range Saturday created thin, soft slabs in the alpine 10 to 20cm deep.

Use caution in lee areas. Recent wind loading has created wind slabs.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 21st, 2019 4:00PM