Regions
Banff Yoho Kootenay.
While the windslabs are getting older, they form a reactive slab over the deep persistent layer.
Weather Forecast
Expect the light winds to shift to the North tonight as arctic air pushes south into the region Friday evening. This will squeeze a few more flakes of snow out of the clouds and drop temperatures a few 4 or 5 degrees for a high of around -8C at 2000m Saturday.
Snowpack Summary
5cm of new snow now buries surface hoar, thin suncrusts, and previous wind effect. Aging windslabs sit over a faceted midpack above the october 26 facet and crust interface generally found 10 to 30 cm above the ground.
Avalanche Summary
Lake Louise reported a sz 2 slab failing on the October 26 layer on the N aspect of Whitehorn. While efforts yesterday had failed to initiate an avalanche higher in the start zone, a 1 kg charge placed lower did the trick today with the thought that winds strong winds had created the slab lower in the start zone instead of the immediate lee.
Confidence
Due to the number of field observations
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.