Regions
Banff Yoho Kootenay.
While human triggering is likely at treeline and above, it is still essential to manage your exposure to avalanche terrain at lower elevations: natural avalanches reaching valley bottom trails are still considered possible.
Weather Forecast
Expect 5 to 10 cm to arrive starting Friday night through Saturday as winds shift from South back to West and climb into the moderate range. Temperatures will cool to -15C values in the ALP Sunday morning with some clearing expected before the cycle repeats: winds shift back to a light South flow bringing warming and a bit more precip for Monday.
Snowpack Summary
100cm of dense, rounded snow comprises the upper half of the snowpack and sits on a very weak base of depth hoar. This unstable structure produces consistent, sudden collapse test results in the depth hoar layer approximately 60cm from ground. Two shears persist near the surface down 15 and 35cm indicating lingering instability in the storm snow.
Avalanche Summary
The natural activity has begun to diminish over the last few days however daily reports of activity continue to come in with a sz 2.5 reported on the NE aspect of Mt Fatigue today. It appears to take only very small inputs of sun, wind or precip to trigger natural events and artificial / human triggering should be considered likely.
Confidence
Intensity of incoming weather systems is uncertain on Friday
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.