Avalanche Forecast
Issued: Jan 27th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Deep Persistent Slabs and Wind Slabs.
tim haggarty,
Parks Canada
With significant winds transporting snow to form wind slabs in the alpine, the likelihood of triggering serious slabs on the persistent and deep persistent layers is on the rise.
Summary
Weather Forecast
Light snowfall is expected Tuesday however amounts will favor the West side of the divide. Watch for winds to peak at strong in the alpine. Snowfall for Wednesday will be lighter however watch for alpine winds to reach extreme. By the end of the day Thursday, a significant system is expected to reach the forecast region.
Snowpack Summary
Recent wind slabs can be found near ridge-tops. There is 40-80 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 . A size 2.5 Na was observed today on the S side on Mt Lipalian that looks 40-60 deep likely indicating a failure on the Dec 31 persistent layer. The forecasting trip to Takakkaw falls area saw few small wind slabs in the alpine.
Confidence
Intensity of incoming weather systems is uncertain on Tuesday
Problems
Persistent Slabs
The late December layer of surface hoar, facets or sun crust is buried 40-80cm throughout the region and produces variable results depending on location and what crystal form is present. Be suspicious on steep solar aspects and look for surface hoar.
- Dig down to find and test weak layers before committing to a piece of terrain.
- If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
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. Be cautious with snowpack depths below 2m by choosing conservative terrain: modest angle and supported shape
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
- Avoid shallow snowpack areas where triggering is more likely.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Fresh wind slabs will continue to develop over the next several days with incoming snow and moderate to extreme winds expected in the alpine.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Use caution in lee areas. Recent wind loading has created wind slabs.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 28th, 2020 4:00PM
