Regions
Banff Yoho Kootenay.
Good skiing West of the divide in sheltered areas. Avoid thin areas in big alpine features as the basal layer can still be triggered. SH
Weather Forecast
Light N winds Sunday with a mix of sun and cloud and a trace of snow. Temperatures will again be in the minus 20's in the mornings, and highs in the -10 to -15C range.
Snowpack Summary
5-15cm of snow over the Jan 30th surface hoar/sun crust layer. Surface hoar most prominent at treeline and below. In Yoho today, thin wind slabs (15cm) over 5cm sun crust on steep S aspects reactive to skier triggering. The basal facets remain weak, but the overall snowpack is gaining strength. Glacial coverage very thin for this time of year.
Avalanche Summary
One size 2 natural cornice triggered avalanche on a SE aspect in Yoho occurred within the last 48 hours. This was a thin slab in extreme terrain.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.