Strong winds are forming wind slabs in leeward areas at upper elevations. Avoid pillows of stiff or chalky looking snow, and be wary of lingering under overhead hazards such as cornices which may be large and fragile.
Weather Forecast
TONIGHT: Flurries. Accumulation trace. Ridge wind moderate to strong, west. Temperature near -10. Freezing level lowering to valley bottom.WEDNESDAY: Mix of sun and cloud, light flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature near -4. Freezing level rising to 1000 m.THURSDAY & FRIDAY: Mostly cloudy, flurries heaviest overnight Thursday. Accumulation up to 5 cm. Ridge wind moderate, southeast easing on Friday. Temperature high near 0, low near -8. Freezing level rising to 1500 m on Thursday.
Avalanche Summary
Monday there were reports of 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.
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
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.