Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.
Consistently strong winds remain the theme in the alpine and at treeline. Be wary of any wind loaded slopes, and watch for wind loading at upper elevations. Wind slabs also have the potential to step down to the basal weak layer resulting in larger avalanches.
With the short days, get out early and get home early.
Confidence
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Avalanche Summary
A large natural avalanche was observed in the alpine on Mount Fairview on Friday. Additionally, there have been natural, human and explosive triggered avalanches at the Lake Louise and Sunshine ski hills up to size 2 within the last few days. Wind slab has been the primary avalanche problem, however there are still avalanches stepping down to the deep persistent weak layer at the base of the snowpack.
Snowpack Summary
Wind slabs continue to build in alpine and exposed treeline areas with mod-strong SW winds. In isolated areas at treeline these slabs may be sitting on the Dec 14 surface hoar. Below this is 20-40 cm of snow from early Dec. This includes a rain crust up to 7 cm thick that exists as high as 2300 m, and is more prevalent in the south part of the forecast area. The base of the snowpack is a mix of surface hoar, basal facets and a crust from late Oct. Treeline snow depths range from 50-90 cm.
Weather Summary
Monday will bring a mix of sun and cloud with possible light flurries west of the divide. Ridgetop winds will increase into the moderate to strong range out of the southwest on Sunday night and stay elevated through Monday.
The alpine high is forecast at -3°C and freezing levels will remain at valley bottom.
For more information, click Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Avalanche Problems
Wind Slabs
Winds remain moderate to strong out of the SW, creating fresh wind slabs in alpine and exposed treeline terrain. These slabs will likely be sensitive to human traffic in steep terrain. In isolated areas at treeline and below the wind slabs may sit over a surface hoar layer from Dec 14.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Deep Persistent Slabs
The bottom of the snowpack is weak and consists of layers of surface hoar, facets, depth hoar, and occasionally a crust. Natural and human triggering of this deep persistent layer remains possible, and avalanches on this layer have potential to run further than expected due to the weak snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5