Regions
Northwest Inland.
Confidence
Poor - Due to limited field observations
Weather Forecast
Wednesday: High pressure moves into the region gradually pushing out the low. Light snowfall amounts accompanied by NW ridgetop winds near 55km/hr. Alpine temperatures near -6.0 and freezing levels around 600 m. Thursday: Upper trough embedded in the flow causing unsettled conditions. Snow amounts 5-10 cm accompanied by moderate ridgetop winds from the West. Alpine temperatures near -5.0 and freezing levels rise to 700 m.Friday: Unsettled conditions continue. Snow amounts 5 cm with ridgetop winds light from the SW. Alpine temperatures -4.0 and freezing levels rising to 900 m.
Avalanche Summary
Loose dry sluffing from steep terrain. SSL forming, Skier triggered slab produced a size 2.0 on a SE aspect near 1400 m.
Snowpack Summary
New storm snow is building over a variety of old surfaces including old wind slabs, scoured thin slopes, blue ice, thin melt-freeze crusts and surface hoar. The new storm snow may have a poor bond with the old surfaces buried below.The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall and larger amounts of new storm snow.
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.