Recent new snow combined with wind has promoted wind slab development as well as cornice growth. As the clouds part in the coming days remember that the sun packs a punch this time of year.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
MONDAY: Mix of sun, cloud and isolated flurries / Light to moderate west wind / Alpine temperature -9 TUESDAY: Mix of sun, cloud and isolated flurries / Light to moderate west wind / Alpine temperature -8 WEDNESDAY: Mix of sun, cloud and isolated flurries / Light southwest wind / Alpine temperature -8
Avalanche Summary
Over the past week there have been reports of both natural and skier triggered loose dry avalanches in steep terrain to size 1.5.
Snowpack Summary
10-25 cm of new snow falling Friday night, brings accumulated storm snow total to 25-40cm. This new snow covers previously wind-scoured, westerly slopes and old hard and soft wind slabs on leeward, easterly alpine and treeline slopes. Beneath these old wind slabs lies a well-settled mid-pack. The lower snowpack is generally weak with two primary concerns that are widespread:A widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.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.