Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
The degree the hazard increases greatly depends on how much snow we receive. The greatest amount of snow is expected in the Northern part of the region and along the Divide and west. Watch for building hazard through the day with strong winds forecast.
Confidence
Low
Avalanche Summary
No new avalanches were observed on Friday.
The common theme from avalanches over the week was small avalanches that then gouged down to basal facets and ran further than expected. Lake Louise got two explosive-triggered avalanches in a steep N to E aspects, failing on the Nov 9 weak layer 40 cm above the ground. The snowpack foundation is weak.
Snowpack Summary
Expect the hazard to increase through Saturday as new snow accumulates and the strong to extreme winds create easily triggered surface slabs; some may fail on the ground.
As of Friday, the snow surface is a mix of sun crust, wind crust, and facets. This overlies a mostly faceted snowpack 40-90 cm deep with two weak layers near the base (Oct 20 and Nov 9 crusts). These crusts continue to produce isolated avalanches.
Weather Summary
We are on the southern edge of a warm Atmospheric River that will spill into Alberta Friday night and all day Saturday. Expect strong W to SW winds (40-60 km/hr) and 5-15 cm by the end of Saturday and another 5-10 cm Saturday night. The greatest amounts will be in the northern part of the region, along and West of the Continental Divide. Freezing levels should be at the valley bottom (1400 m).
Terrain and Travel Advice
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Deep Persistent Slabs
This layer will become more reactive with increased loading from new snow and wind, or surface avalanches that step down. The October and November crusts, on north and south aspects respectively, were still producing isolated slab avalanches down about 50-80 cm over the week.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 2.5
Wind Slabs
Windslabs will build with incoming snow, strong-extreme winds, and relatively warm temperatures. The degree of formation will depend on snow amounts received and wind transport of the new snow. Newly formed slabs sit on a weak foundation and are expected to be reactive to triggering.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood: Likely
Expected Size: 1 - 2
Loose Dry
Incoming snow and strong winds will result in a loose dry problem in steep extreme terrain.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Likely
Expected Size: 1 - 1.5