Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Human-triggered avalanches are likely in any avalanche terrain where a slab sits over the deeper facet layers. Remote triggering of these weak layers is also possible.
This is not a problem you can outsmart and it will linger for the foreseeable future. The ways to reduce risk are through avoidance of avalanche terrain or choosing small slopes where the consequences of an avalanche will be smaller.
Start the New Year with patience and wait for things to improve.
Confidence
High
Avalanche Summary
A skier triggered size 2 avalanche in the Emerald Lake slide path occurred Saturday on the basal facets resulting in serious injuries. Several other human triggered and remotely triggered slabs on this basal interface from size 2-2.5 have also occurred in the past three days. Avalanche explosive control over the last week produced large avalanches up to size 3 in many different areas on 95% of the shots. Some were initiated on the Dec. 17 interface but most stepped down to the basal facets.
Snowpack Summary
10-20 cm of soft surface snow in sheltered areas. Below this a settled slab 25-60 cm thick sits over a weak layer of facets and surface hoar from Dec 17. Below this another 20-40 cm of facets sit over the weak Nov 16 interface, with the bottom 20-50 cm of the snowpack made up of weak facets and depth hoar. Total snowpack depths of 80-140 cm at treeline.
Weather Summary
Some light flurries overnight into Sunday with a few cm's of accumulation in the West near the divide. Sunday should be a mix of sun and cloud. Winds will be in the moderate range from the W-NW becoming light on Sunday. Temperatures will remain steady in the -10 to -14°C range.
Terrain and Travel Advice
- Uncertainty is best managed through conservative terrain choices at this time.
Avalanche Problems
Deep Persistent Slabs
Much of the bottom half of the snowpack is very weak and faceted. Avalanches have been occurring on this layer, or starting higher in the snowpack and "stepping down" to the basal facets causing large avalanches. Anywhere a slab is present over the basal facets we expect human triggering to be likely and remote triggering to be possible.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 3
Persistent Slabs
Slabs typically 25-60cm thick sit over a Dec. 17 weak layer of facets that was on the surface during the prolonged deep freeze. If initiated, the big concern is that it can step down to the deeper weak layers resulting in large avalanches. Below treeline the problem exists anywhere there is a slab overlying the deeper weak layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2