Avalanche Forecast
Regions: Banff Yoho Kootenay.
Rapid loading has created fresh slabs and cornice growth and has overloaded the persistent and deep persistent layers at upper elevations while rain has weakened the snowpack at lower elevations. A widespread natural avalanche cycle has been observed
Weather Forecast
After 24hrs of rain to 2000m, temperatures have begun to drop late in the day Saturday and are expected to reach -10C in valley bottoms overnight. Mountain top winds will diminish to strong values while precipitation will fade to light flurries through mid day Monday before some clearing can be expected.
Snowpack Summary
Wind and storm slabs have developed with strong SW winds, 30 to 70 cm of snow above 2000m. Rain has soaked the snowpack at lower elevations. The Dec 31 layer of facets, surface hoar and sun crust is currently down 40-100 cm. The deep persistent basal layer sits 20 to 40 cm above the ground and is more developed in shallow snowpack areas.
Avalanche Summary
A widespread avalanche cycle to sz3.5 has been observed along the roadways of the 3 national parks today. Large wet piles of debris have bee observed to the tops of run outs and bottom of tracks. Although start zones have largely been obscured, involvement of the persistent and deep persistent layers has been seen along the flanks of several events
Confidence
Due to the number of field observations
Avalanche Problems
Storm Slabs
Storm and wind slabs developed rapidly in the past 24hrs along with fragile cornice growth. Despite the cooling trend, expect these slabs to remain sensitive to failure over the short term with continued natural activity expected.
- 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 is now down 50 to 100cm making these slabs ripe for human triggering.
- Dig down to find and test weak layers before committing to a line.
- Choose low angle and supported terrain. Avoid large features.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Very Likely
Expected Size: 2 - 3
Deep Persistent Slabs
With start zones loaded and the snowpack weakened by rain at lower elevations, avalanches can easily scrub to ground and entrain mass as they move though the track and into the run out zone. Many slides have reached valley bottom in the past 24 hrs.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 2.5 - 4