Regions
Banff Yoho Kootenay.
New snow, strong winds and a weak base in the snowpack mean that this weekend is a good time to stay out of avalanche terrain! Enjoy the fresh snow. CJ
Weather Forecast
A strong pacific system is forecast to arrive tonight with moderate to strong W winds and temperatures between -5'C and -10'C. 15-25cm of new snow is expected by Saturday night with an additional 5-10cm each day through Monday.
Snowpack Summary
5cm new snow and gusty SW winds up high today. East of the divide a weak mid pack sits over an even weaker basal facet layer with moderate sudden collapse results in the basal facets. West of the divide the snowpack is deeper and more supportive but the weak basal facets remain the main concern.
Avalanche Summary
While no new avalanche activity has been observed over the past 48hrs, whumphing on lower angled terrain indicates the continued potential for skier triggered slab avalanches on the basal facets. Expect increased avalanche activity to begin with the arrival of the new snow tonight!
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.