Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Increasing winds on Thursday and Friday will move loose surface snow around in alpine terrain. Although we don't expect a large loose dry cycle, this could be enough of a trigger for one of the deeper weak layers.
Confidence
Low
Avalanche Summary
Lake Louise patrol noticed a size 1 windslab that failed naturally overnight. Sunshine patrol was able to trigger one size 2 deep slab with a cornice shot with explosives. Parks forecasters noted several large whumphs in the Sunshine Backcountry today.
Snowpack Summary
20-60 cm of snow has formed a slab over a very weak base consisting of facets. Thin crusts can be found on the facet interface at lower elevations and on solar slopes. Expect to find lingering wind slabs at higher elevations. Snowpack depths at treeline range between 60 and 120 cm.
Weather Summary
Thursday: Alpine highs -8 to -15, lows -20. Winds moderate NW. No precipitation.
Friday: Alpine high -12, low -20. Winds moderate to strong W. No precipitation
Saturday: Alpine high -20, dropping to -24 throughout the day. Alpine winds dropping to light NE. 2-4 cm of snow.
Terrain and Travel Advice
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- Uncertainty is best managed through conservative terrain choices at this time.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avalanche Problems
Deep Persistent Slabs
A 20-60 cm slab has formed over the very weak basal facets, with thin crusts at the interface at lower elevations and on some solar slopes. Human triggering is likely on any steep slopes where a cohesive slab of snow is found. This problem will remain for the foreseeable future.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5
Wind Slabs
Increasing winds on Thursday and Friday may create new windslabs or add load to older ones. If triggered, it is likely that these will step down to the deep persistent weak layer resulting in a larger avalanche.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1.5