Regions
Banff Yoho Kootenay.
Temperatures will cool off Sunday and conditions will improve as this happens. Watch for local wind slab formation at upper elevations. SH
Weather Forecast
15-20 cm in the alpine can be expected in most of the forecast region.(Less in the Banff area) by Sunday AM. This is a quick moving system which will settle down Sunday morning. Freezing levels to valley bottom and alpine highs of -8C for Sunday.
Snowpack Summary
Rain at lower elevations (below 2000m) has saturated thin snowpack areas. 15-20cm and mod-strong West winds are expected by Sunday morning, which will form fresh wind slabs over previous wind slabs and hard surfaces in exposed lee terrain. The basal depth hoar/facets are bridged by the settled midpack, but caution is advised in thin snowpack areas.
Avalanche Summary
No new avalanches observed or reported today.
Confidence
Forecast snowfall amounts are uncertain on Sunday
Problems
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.
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.