Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Conservative terrain selection is essential to manage the deep persistent slab problem.
Use caution on any steep slopes where a cohesive slab is found.
The consequences of getting caught are high right now with thin snowpack values providing poor coverage for rocks and logs.
Confidence
Moderate
Avalanche Summary
Following explosive control efforts on Saturday, SSV snow safety triggered a sz 2.5 slab at 2300m on a NW aspect 40 to 130cm deep and 50-60m wide running 240m on the basal facets. Further explosive control work produced an additional sz 2 deep persistent slab 40m wide at 2700m on a NW aspect. A sz 2 windslab off of Crowfoot Mountain on a NE aspect at 3000m was reported to have run 700m and over the ice climb located near the toe of the glacier
Snowpack Summary
20-60 cm of snow has formed a soft 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. Recent moderate southwest winds have formed slabs at higher elevations. Snowpack depths at treeline range between 60 and 120 cm.
Weather Summary
A ridge has formed over British Columbia with a Pacific low pressure system currently swinging north of the ridge into northern Alberta.
Very light north winds bringing colder alpine temperatures (-15- to-20C) can be expected overnight Monday before the low starts its descent through the prairies Tuesday. Moderate to strong northerly winds, some light snowfall and alpine high temperatures near -10C can be expected Tuesday afternoon.
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 soft slab has formed over the very weak basal facets, with thin crusts at the interface at lower elevations and on some solar slopes. Whumpfing and cracking have been frequently observed in many locations over that last several weeks and human triggering should be considered 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
10-25 cm of snow fell over the past week and moderate S-W winds formed soft wind slabs in lee areas. These slabs are relatively soft and small but the major concern is that if triggered, these may step down to the weak basal facets resulting in larger avalanches. As north winds pick up Tuesday watch for a different loading pattern and possibly some new slab formation.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2