Avalanche Forecast
Regions: Banff Yoho Kootenay.
Two problem snowpack layers vary a great deal throughout the forecast region. Although natural avalanche activity has tapered, human triggering is still considered quite possible. Make conservative terrain choices and investigate the snowpack closely
Weather Forecast
Moderate to strong winds are expected to continue Sunday night as a cold front passes the area bringing trace amounts of snow. As a second frontal system crosses the divide Monday, winds are expected to remain elevated. Light precip will continue Monday amounts may increase on Tuesday but will favor the West side of the divide.
Snowpack Summary
Recent wind slabs can be found near ridge-tops. There is 40-60 cm above the Dec 31 layer of facets, surface hoar and sun crust which produces variable test results through the region. 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
A large natural avalanche over Cascade waterfall occurred Friday failing on the basal facets/depth hoar (possibly triggered by warm temperatures and solar input). Past 72hrs: a wind slab stepped down to the persistent layer on Mt Bourgeau- sz 2.5, and two explosive triggered avalanches stepped down to basal layers on the north side of Whitehorn.
Confidence
Intensity of incoming weather systems is uncertain on Tuesday
Avalanche Problems
Persistent Slabs
The late Dec layer of surface hoar, facets or sun crust is buried 40-60cm throughout the region and producing variable results depending on location and what crystal form is present. There is still high uncertainty as to how reactive this layer is.
- If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
- Dig down to find and test weak layers before committing to a piece of terrain.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 2.5
Deep Persistent Slabs
In the past week we have seen several avalanches initiate or step down to this deep persistent layer of facets, depth hoar and crusts. Conservative terrain choices are your best defence as this problem is almost impossible to forecast.
- Avoid shallow snowpack areas where triggering is more likely.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 2 - 3.5
Wind Slabs
Wind slabs exist near ridge-tops. With elevated winds continuing overnight Sunday thought Tuesday, expect these slabs to develop.
- Use caution in lee areas. Recent wind loading has created wind slabs.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2