Regions
Northwest Inland.
Confidence
Poor - Forecast snowfall amounts are uncertain
Weather Forecast
Monday: A low pressure system over Gulf of Alaska will move onto the North Coast. Precipitation moderate-heavy (15-35 mm) accompanied by strong-extreme ridgetop winds from the NW. Alpine temperatures rising to -2.0 and freezing levels near 700m. Tuesday: An intense warm front will continue to bring moderate precipitation (5-15 mm). Ridgetop winds will switch and blow strong-extreme from the West. Alpine temperatures near -1 and freezing levels up to 1000 m. Wednesday: An upper ridge continues to build generally bringing dryer conditions during the day. Alpine temperatures near -4.0. Ridgetop winds blowing form the SW in the light ranges.
Avalanche Summary
On Saturday, loose dry sluffing was reported from steep terrain.
Snowpack Summary
New storm snow is building over a variety of old surfaces. These include 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
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.