A strong southeast flow is expected to bring more snow beginning late Thursday and into Friday. Amounts are uncertain but expect to find new storm slabs building especially at upper elevations.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A strong southeast flow system will bring snowfall beginning late Thursday afternoon. Amounts are uncertain but accumulations of more than 15 cm by Friday morning may be possible in some areas.TONIGHT: Flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature near -9. Freezing level lowering to valley bottom.THURSDAY: Snow increasing in the afternoon and overnight. Accumulation 10-15 cm. Ridge wind light to moderate, southeast. Temperature near 0. Freezing level rising to 1400 m.FRIDAY: Mainly cloudy, flurries increasing overnight. Accumulation 2-10 cm. Ridge wind light, east. Temperature near -4. Freezing level 600 m.SATURDAY: Mainly cloudy, light flurries. Accumulation trace. Ridge wind light, northeast. Temperature near -5. Freezing level 600 m.
Avalanche Summary
There have been no new avalanches reported since Monday when both natural and skier triggered loose dry avalanches in steep terrain, as well as skier and explosive triggered storm slab avalanches up to size 1 were reported.
Snowpack Summary
Strong to extreme winds have scoured windward slopes and formed cornices and hard and soft wind slabs on (downwind) alpine and treeline slopes. These wind slabs overlie various surfaces, including older hard wind slabs, crusts, facets and spotty surface hoar.The lower snowpack is weak with two primary concerns that are generally widespread:1) A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) A rain crust with sugary facets buried in late November near the bottom of the snowpack.
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.