Avalanche Forecast
Regions: Banff Yoho Kootenay.
Avoid all avalanche terrain Saturday. With the incoming storm, we expect the natural avalanche activity to increase. Some will run well into the valley bottom, and possibly to the end of the paths.
Weather Forecast
Overnight Friday, we expect 20-30cm (highest amounts Lake Louise and North) and another 30-50cm on Saturday with strong to extreme winds & 2000m freezing levels. These warm temperatures will mean rain at lower elevations. The storm passage mid-day Saturday is marked by dropping temperatures (to -15-20C), decreasing wind, and tapering snow amounts.
Snowpack Summary
Wind and storm slabs are developing over the next 24 hours with strong SW wind, 40-80 cm of snow, and rain below 2000 m. We expect this to overload the Dec 31 layer of facets, surface hoar and sun crust (currently down 40-80 cm) and/or the deep persistent basal layer. Loose wet avalanches are likely below tree line Saturday morning.
Avalanche Summary
Visibility has been obscured as the "atomospheric river" storm moved into the region this afternoon. We expect natural avalanches to be occurring for the next 24 hours with the onset of wind, snow, rain, and rising temperatures.
Confidence
Avalanche Problems
Storm Slabs
Storm slabs will be developing through the night. This problem also incorporates wind slabs as well as loose dry avalanches in steep terrain, all of which will be increasing in size and likelihood as the storm tracks through the region.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely - Certain
Expected Size: 1 - 2.5
Persistent Slabs
This layer of surface hoar, facets and crusts was 50 to 80cm down prior to the storm. With forecasted loading from snow, rain, and wind over the next 24 hours, we expect to see an increase in avalanche activity.
- If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Very Likely - Certain
Expected Size: 2 - 3
Deep Persistent Slabs
With the large load expected over the next 24 hours, we expect very large avalanches either starting or stepping down to the deep basal facets and depth hoar. Avalanches are expected to reach valley bottom and possible to extreme runouts.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 2.5 - 4