Regions
Banff Yoho Kootenay.
Warm temperatures and rain will destabilize the already weak snowpack especially at lower elevations. Ice climbers in particular should stay out of low elevation gullies.
Weather Forecast
Strong southwesterly winds, light precipitation, and warm temperatures with freezing levels to 2000m will dominate on Wednesday and Thursday. Temperatures will drop and winds will ease on Friday.
Snowpack Summary
Warmer daytime temperatures are promoting settlement of the upper snowpack and creating more of a slab over the basal facets/ rain crust 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
Avalanche control work today at the Lake Louise Ski area triggered avalanches to size 2 in terrain that had been previously controlled. This demonstrates that the weak layers at the base of the snowpack were not cleaned out in last weeks avalanche cycle and will likely be with us for some time.
Confidence
Timing, track, or intensity of incoming weather system is uncertain 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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.