Avalanche Forecast
Regions: Banff Yoho Kootenay.
Avalanche Control is planned for Mt Whymper, the Sunshine Village access road, Mt Field and Mt Stephen Sunday March 8.
No activities in these areas please.
Weather Forecast
Winds dropped of last night but snow - pushing in from the prairies - continues to fall Saturday with another 5cm expected overnight. The formation of a ridge Sunday should push out a few remaining flurries and usher in some clearing for Monday. Light to moderate winds are expected in the alpine until Tuesday when and increase has been forecast.
Snowpack Summary
50-70 cm has fallen in the past week with strong Westerly winds. Expect to find wind slabs in lee areas and exposed terrain features. The recent snow is piling up and buries sun crust on steep solar aspects and the Feb 1 crust in isolated areas up to 1900m. In thin snow pack areas a dense mid-pack sits over a weak, faceted base.
Avalanche Summary
Reports of two deep persistent slab avalanches on Thursday in the alpine from South to East aspects; a sz 3 triggered by cornice fall and a sz 2.5 from explosive avalanche control.
A further report of an explosive controlled sz 2.5 on deep persistent layers on Saturday. We suspect a limited natural cycle is ongoing.
Confidence
Due to the number of field observations
Avalanche Problems
Wind Slabs
Expect to find wind & storm slab formation on lee aspects and open areas from the alpine to tree line. 10-15cm of fresh snow may cover these now making them more difficult to detect. Cornices should be considered suspect due to recent growth.
- Watch for fresh wind slabs on exposed lee slopes and open areas at all elevations.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2.5
Loose Dry
Sluffs will fail easily with skier traffic in steep terrain and are failing naturally in very steep terrain. Use caution in gully features or in cliffy terrain where these can have serious consequences.
- Good group management is essential to manage current conditions safely.
- Sluffs may trigger deeper instabilities.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 1.5
Deep Persistent Slabs
With recent loading and smaller natural avalanche activity ongoing, the potential for avalanches on the basal facets is on the rise. These are most likely in areas with a thin snowpack (<130cm) where the basal facets and depth hoar are prominent.
- Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5