Avalanche Forecast
Regions: Bonnington, Crawford, Grohman, Kokanee, Kootenay Boundary, Kootenay Pass, Moyie, Norns, Retallack, Rossland, St. Mary, Valhalla, Whatshan, Ymir.
Storm snow remains triggerable at higher elevations. Uncertainty around a buried weak layer is best managed through conservative terrain choices.
Confidence
Moderate
Avalanche Summary
No new avalanches were reported this weekend.
Many storm slab and loose wet avalanches released during the intense rainy conditions earlier this week. Natural avalanche activity likely tapered on Friday.
We're uncertain on whether avalanches could still release on the surface hoar layer described in the Snowpack Summary, so travel cautiously until there is evidence it is bonding or has been destroyed.
Snowpack Summary
25-50 cm of snow sits on a 3-15 cm melt-freeze crust. Below, previously moist snow from the rain event seems to have mostly refrozen.
A layer of surface hoar buried ~45 cm has been observed to have miraculously survived the rain in some areas. It may have been largely cleaned out by avalanches during the recent storm, but could linger in isolated features. Triggering this layer is less likely in areas where the overlying crust is thicker and more supportive. We recommend treating this layer as suspect while we await more observations.
Snow depth is generally 70-110 cm at treeline, tapering quickly below. The mid and lower snowpack may contain a weak facet layer in shallower areas.
Weather Summary
Sunday Night
Cloudy. 5-7 cm of new snow. Light to moderate southwest ridgetop wind. Treeline high temperature around -6°C.
Monday
Partly cloudy. No new snow expected. Light north ridgetop wind. Treeline temperature around -5°C.
Tuesday
Mix of sun and cloud. No new snow expected. Light to moderate southwest ridgetop wind. Treeline temperature around -4°C.
Wednesday
Mix of sun and cloud. No new snow expected. Moderate to strong south ridgetop wind. Treeline temperature around -6°C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Closely monitor how the new snow is bonding to the old surface.
- Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
- Uncertainty is best managed through conservative terrain choices at this time.
- Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.
Avalanche Problems
Storm Slabs
Storm slabs may remain triggerable by riders, especially where wind has redistributed the recent snow into leeward terrain features on north and east aspects
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
This surface hoar layer was seen after the rain storm in some areas, 4-20mm big. As the moisture in the snowpack migrates and freezes, the weak layer may melt or bond, and crusts above it may become more robust, making it harder to trigger.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 1.5 - 2.5