Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
New snow has refreshed the skiing but also created a new layer of concern. We expect this to be most reactive in alpine/ treeline terrain where the wind has created a slab above it, so heads up if you are seeking out this terrain!
Confidence
Moderate
Avalanche Summary
Clear skies today revealed more evidence of a natural avalanche cycle over the last few days:
A team in Field area reported several slabs on below treeline fans near the ice climbs of Twisted and Guinness Gully
A team in the Sunshine backcountry reported 2 size 2 slabs on steep north facing alpine/ treeline terrain. These were likely triggered by sluffing/ cornices and stepped down to the basal layers
A size 2 was also observed on an alpine S aspect failing above the ground
Snowpack Summary
20-30 cm of recent snow has been blown by S/SW winds into windslabs in exposed alpine and treeline locations. In sheltered areas, non-wind effected snow sits on a layer of facets, suncrust and isolated surface hoar that was buried on Dec. 7th. Below this is a weak and facetted, early season midpack with two crust/facet layers near the bottom of the snowpack (Nov. 9th and Oct. 20th interfaces). Total snowpack depths at treeline are 50-80 cm.
Weather Summary
A ridge of high pressure sits over the area bringing cooler air and stable weather for a few days. Skies should be mostly clear with few clouds, light NW winds and high temperatures of ~ -5 to -10. Another system offshore may bring some light precipitation starting Wednesday evening or Thursday.
Terrain and Travel Advice
- Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Wind Slabs
Moderate SW/W winds during the storm have created windslabs in lee features in the alpine and at treeline. These have been reactive to hand charges and ski cuts at local ski hills as well as several naturally triggered avalanches over the last few days.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
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: Possible - Likely
Expected Size: 1.5 - 2.5