Regions
Banff Yoho Kootenay.
The storm slab continue's to be reactive, producing large avalanches and remote slab releases.
Weather Forecast
A pulse of precipitation is expected tonight with 5 to10cm and moderate winds from the west, temperatures will remain below freezing with lows in the -20's. No significant low pressure systems are expected this week, but expect small convective pulses to bring in some snow.
Snowpack Summary
40-50cm of storm snow has developed into a touchy storm slab that is sensitive to triggers at treeline and above. This sits over a supportive mid-pack, with the lower half of the snowpack consisting of weak facets and depth hoar. There is isolated wind effect near ridge crests only; the notable observation is the lack of wind effect.
Avalanche Summary
Avalanche control on Mt Whymper and Mt Simpson today. On Whymper results were similar to previous control this week, touchy storm slabs producing avalanches to size 3 as well as remote avalanches on adjacent slopes. Further south at Mt Simpson results were less dramatic, mostly smaller soft slab releases with one size 2.5 from a cornice release.
Problems
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.
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.