Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
A sensitive weak layer (Dec 7) has just been buried by the recent storm snow. The new snow is bonding poorly to this interface, yet no widespread avalanche cycle was observed. The surface snow mostly remains cold and dry, but in locations where the wind has created a surface slab, watch out as these spots will be easily triggered.
Confidence
Moderate
Avalanche Summary
Good visibility on Sunday and most reports have not observed much in the way of fresh avalanches except where you would expect them. Several storm avalanches up to size 2 out of steep terrain on Bow Peak (Grandaddy area), several small storm slabs at the LL and SSV ski areas, but no large natural avalanches reported in the backcountry (yet).
Snowpack Summary
Storm snow totals of 23-32 cm fell across the region, sitting on a freshly buried weak layer (Dec 7) that will be the one to watch for a few days. This new snow won't bond well to Dec 7 (facets and crust), and the key will be to watch for slab development in the surface layers - wherever the wind has stiffened up the snow, watch for an easily triggered windslab. Any avalanches starting in the surface layers have the potential to step down to the facets near the ground.
Weather Summary
The weekend storm has passed, followed by a clearing trend as a ridge of high pressure moves over the area, cools the air and stabilizes the weather for a few days. Monday and Tuesday should be mostly clear with few clouds, light winds and high temperatures of -7. Another system offshore should change this pattern by the second half of the week.
Terrain and Travel Advice
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Wind Slabs
Eight hours of moderate SW winds overnight on Saturday have probably created windslabs in exposed alpine areas. We have no reports of this yet but expect that 30cm of storm snow and moderate winds will have created this problem in alpine and some treeline areas.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Deep Persistent Slabs
Two weak layers near the base of the snowpack (Oct 20 and Nov 9) are producing isolated slab avalanches down about 50-80 cm. Mostly observed on steep NW-NE aspects. Any surface windslabs have the potential to step down to this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 2.5