Regions
Banff Yoho Kootenay.
Reports of skier triggered windslabs and explosive triggered slabs on the October 26 Crust and Facet Deep Persistent layer continue to come in. Skiers and climbers should be taking a conservative approach on their early season trips.
Weather Forecast
Although a ridge with dominate the weather until at least late Tuesday, it looks like there will be lingering cloud. There is some potential for an alpine temperature inversion however both treeline and alpine temperatures are expected to remain below freezing. Watch for alpine winds to pick up Tuesday.
Snowpack Summary
In the alpine, 20-50cm with variable wind effect sits on the Oct.26th temperature crust which can be found mainly on shaded aspects treeline and above and is a few cm thick above weak facets. Total snowpack depths are 60-120cm+ in the alpine, tapering dramatically at treeline to below threshold values for avalanche below treeline.
Avalanche Summary
Explosive control work at Sunshine Village produced a sz slab on the October 26 crust in the Delirium Dive and the snow safety team at Lake Louise were working to clean up lingering windslabs. Over the last there have been several instances of natural and remotely triggered avalanches on the October 26 crust through the region.
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.