Avalanche Forecast

Issued: Jan 21st, 2018 4:16PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Enjoy the new snow, but remember that there is enough whumphing and avalanche activity on the mid-pack weak layers to continue with a cautious approach to larger more committing terrain.

Summary

Weather Forecast

We should see some new snow Sunday night and into Monday with models showing between 5-10 cm of snow at treeline. Temperatures will remain below freezing with -10 to -12'C at upper elevations. 3000m winds will be moderate/strong SW Sunday night then dropping Monday. Tuesday sees a slight clearing trend and perhaps some more flurries on Wednesday.

Snowpack Summary

Newly formed wind slabs in immediate lee features at alpine and treeline elevations. In sheltered areas the upper snowpack consists of 20-30cm of soft slab over the Jan 6 surface hoar. The Dec 15 layer of surface hoar and facets is down 40-60 cm and is reactive in snow tests. Below treeline much of the snowpack is facetted with little structure.

Avalanche Summary

Two size 2 slabs triggered by wind loading and cornice failures were observed in the last 24 hours on Quartz Ridge and the 93 North. These both appeared to fail on a mid pack layer of facets. One skier triggered size 1 wind slab was reported in Semi Circular Bowl near Lake Louise. Numerous large sluffs out of steep rocky terrain in the last 36 hrs.

Confidence

Intensity of incoming weather systems is uncertain on Monday

Problems

Wind Slabs

Recent winds and snow have formed wind slabs in immediate lee areas and caused sluffing in steep rocky terrain. Pay attention to the surface texture and local wind transport patterns as these will be the biggest indicator of the wind slab problem.

Use caution in lee areas. Recent wind loading have created wind slabs.If triggered the wind slabs may step down to deeper facet layers resulting in larger avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

The Dec 15 surface hoar/facet layer continues to cause concern with forecasters. Only a few avalanche observations have been reported on this layer recently, but widespread cracking and whumphing is still occurring when traveling in the back country.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Use conservative route selection, choose supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Jan 22nd, 2018 4:00PM