Regions
Banff Yoho Kootenay.
Visibility was poor today, so limited observations on Tuesday. A little bit of new snow with some moderate SW winds has created some small reactive windslabs in the alpine.
Weather Forecast
A warm wet storm is hitting the coast, but we won't get much in the Rockies. We should see another 5-10 cm with mild temperatures by the end of day Thursday with moderate SW winds. Colder air is coming on Friday as temperatures drop to -15 to -20 and winds switch to the NW.
Snowpack Summary
Moderate SW winds and 5-10 cms of new snow has created windslabs in the alpine. These sit on sun crust on steep south and surface hoar on sheltered N aspects. The Oct 26 crust is found ~10-30 cm above the ground with large facets growing both above and below it. The snowpack averages 40-85 cm at 2200m across the region and is weakening as it facets
Avalanche Summary
Sunshine Village ski patrol was reporting thin soft windslabs in immediate lees on Tuesday. These were touchy, but small and low consequence at this time. No other avalanches observed or reported, but visibility was limited.
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.