Avalanche Forecast
Regions: Bonnington, Crawford, Grohman, Kokanee, Kootenay Boundary, Kootenay Pass, Moyie, Norns, Rossland, St. Mary, Valhalla, Ymir.
Expect to find fresh wind slabs at higher elevations, but buried weak layers remain the primary concern. The potential for large and destructive avalanches continues.
Confidence
Moderate
Avalanche Summary
Last reported avalanches are from explosive control work on Thursday, producing slabs up to size 4.
Recent avalanches have been large and destructive, running full path. Check out the photos below for an explosive triggered avalanche near Nelson, and a rider triggered avalanche in the Bonningtons on Tuesday. While natural activity appears to have tapered off, human triggering is still a concern and will likely produce a high consequence avalanche.
Snowpack Summary
Storm totals are expected to reach 10-30 cm by Sunday afternoon, falling on a variety of weak surfaces - a crust on sun affected slopes, surface hoar in sheltered terrain, and wind affected snow in exposed areas.
A widespread crust with weak facets above remains a concerning layer for human triggering. Buried 80-150 cm deep, this layer has produced very large avalanche activity this week.
The snowpack below the crust is generally strong.
Weather Summary
Saturday Night
Cloudy with 5-10 cm of snow. 30-50 km/h southwest ridgetop wind. Freezing levels drop to around 1000 m.
Sunday
Cloudy with 5 to 15 cm of snow. 40 km/h southwest ridgetop wind, gusting to 80 km/h. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.
Monday
Cloudy with 5 cm of snow. 20-30 km/h southwest ridgetop wind. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.
Tuesday
Cloudy with 5-15 cm of snow. 30-50 km/h southwest ridgetop wind. Freezing levels rise to 1500 m, with treeline temperatures around -3 °C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Keep in mind that human triggering potential persists as natural avalanching tapers off.
- Remote triggering is a concern, watch out for adjacent and overhead slopes.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avalanche Problems
Persistent Slabs
While this layer is becoming less likely to be affected by a rider, if triggered, a large and destructive avalanche is likely. Avoid areas where the snowpack thins, like steep, rocky start zones where weak layers are more easily triggered.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 2 - 3.5
Wind Slabs
Reactive wind slabs likely exist on north and east facing slopes around ridgelines. Small wind slabs could step down to deeper weak layers producing very large avalanches.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2