Regions
Banff Yoho Kootenay.
Wind, snow and warmer temperatures are expected between today and the end of the week. Expect the danger rating to rise.
Weather Forecast
The forecast region is expecting an increase in wind velocity from the west starting Tuesday evening, accompanied by light snowfall that will carry through until Wednesday morning. Temperatures will slowly rise to the -5 range at valley bottom in the same time period. A second wave of precip will track through the forecast region late on Friday.
Snowpack Summary
There is 15-25 cm of low density snow at tree line with a thin rain-crust below the storm snow at lower elevations. Some wind effect exists in alpine areas and it is expected to increase. Common throughout the region are the weak facets and depth hoar in the lower half of the snowpack, overlain by a 40-60 cm slab of well settled snow.
Avalanche Summary
No new avalanche activity was observed or reported on Tuesday.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Wednesday
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.