Regions
Banff Yoho Kootenay.
Warmer temperatures and moderate W winds will help create more of a slab over the weak base in our snowpack. Human triggered avalanches remain possible especially in areas with recent wind effect.
Weather Forecast
Mild temperatures, moderate W winds and a few flurries are forecast for tonight with a bit of a clearing trend on Sunday and Monday. Tuesday we may see a few more flurries but accumulations are expected to be minimal.
Snowpack Summary
Warmer temperatures today are promoting settlement of the upper snowpack and creating more of a slab over the basal facets especially in wind affected areas. The lower half of the snowpack is poorly structured, with facets (Nov 24th) below the recent storm snow, thin crusts (Nov 6th) below this, and then depth hoar near the ground.
Avalanche Summary
Little natural activity has been observed recently however explosive triggered slab avalanches up to size 2.5 were reported yesterday from the ski areas with the slab failing on the basal facets and crusts near the ground. These kinds avalanches would result in a dirty, rough ride through scree, rocks and trees and human triggering is possible.
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.