Regions
Banff Yoho Kootenay.
A fairly strong storm system is forecast to arrive for the weekend. While improving the travel conditions, this storm will almost certainly push the avalanche danger to HIGH by Saturday evening. JBW
Weather Forecast
The stronger Pacific System is forecast to arrive mostly on Saturday with a potential for 20-30cm total over Western terrain before the snow ends Monday. Winds may push into the strong range briefly enhancing load.
Snowpack Summary
The winds have been relatively light for the last 24 hrs, and the forecasted push of Pacific moisture has yet to arrive, so the snowpack has not changed much. Windslabs over weak mid pack over very weak base of depth hoar and/or crust is the basic set up. The base is just waiting for some more load before another avalanche cycle begins.
Avalanche Summary
No new avalanche activity has been noted in the last 24 hrs. Whumphing and collapsing on lower angled terrain indicates the potential for skier triggered slides.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Saturday
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.