Regions
Banff Yoho Kootenay.
Although the snowpack continues to stabilize, the Deep Persistent Slab Problem has a significant amount of uncertainty. Deep snowpack areas to the west have a stronger snowpack (eg: Pulpit, Little Yoho). Conditions will deteriorate on Saturday.
Weather Forecast
One more day of high pressure with a light Northwest flow brings mostly sunny skies for Friday with temperatures remaining cool (-10 to -20), but this changes on Saturday as an intense 1-day system will cross the area and deposits 10-20 cm of snow with extreme winds in the forecast (>100 km/hr).
Snowpack Summary
The majority of the BYK region is a 40-50cm slab of stiff snow overlying 40-50cm of weak facets and depth hoar. This nasty combination has been stabilizing over the past few days but continues to produce whumphing and easy test results. Deeper snowpack areas are stronger, but have a 60-80cm slab over top of the Dec10 surface hoar/facet layer.
Avalanche Summary
No new avalanches observed or reported in the Banff, Yoho and Kootenay region on Thursday.
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.