Avalanche Forecast
Regions: Banff Yoho Kootenay.
Conditions will deteriorate through the day Friday with an incoming powerful system. Climbers and skiers should keep it simple by avoiding avalanche terrain and any areas that have overhead exposure like the runouts of large avalanche paths.
Weather Forecast
The first real wave of the incoming Westerly "Atmospheric River" starts Friday peaking on Saturday. Forecasts vary wildly but we can expect 10-30cm Friday (highest amounts Lake Louise and North) and 30-50cm on Saturday with strong to extreme winds and 2000m freezing levels. These warm temperatures will mean rain at lower elevations.Â
Snowpack Summary
Wind slabs are prevalent in the alpine and treeline. There is 40-80 cm above the Dec 31 layer of facets, surface hoar and sun crust which produces test results in the hard range. The bottom layer of the snow-pack consists of weak facets and depth hoar, except for in deeper snow-pack areas (over 2m) where the basal facets are not as prominent.
Avalanche Summary
An increase in natural avalanche activity up to size 2.5 was observed Wednesday. This appeared to be a result of the strong to extreme winds starting late in the morning. With forecasted values of 100kmh winds continuing through the weekend, we can expect more natural avalanche activity to come.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Friday
Avalanche Problems
Storm Slabs
Storm slabs will be developing through the day depending on location. This listed problem also incorporates previous wind slabs as well as loose dry avalanches in steep terrain, all of which will be increasing in size and likelihood.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 2
Persistent Slabs
This layer of surface hoar, facets and crusts can be found 50 to 80cm down and has been showing varied results in snow pack test. With forecasted snow and wind over the next few days we will likely 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: Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
With the large load expected over the next 48 hours, it is plausible we will see an increase in very large avalanches either starting or stepping down to the deep basal facets and depth hoar. Avalanches are expected to reach valley bottom.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 2 - 3.5