Confidence
Fair - Forecast snowfall amounts are uncertain on Sunday
Weather Forecast
Saturday: Light to locally moderate snowfall overnight Friday into Saturday. Freezing level 1600m. Winds light southwest.Sunday: Cloudy with light to locally moderate amounts of snow possible. Freezing level rising to 1800m. winds light west.Monday: Scattered flurries. Freezing level 1500. Winds light to moderate west.
Avalanche Summary
Recent reports from the central part of the region (where the most recent snowfall was intensified) indicate natural and explosives triggered avalanches running in the alpine to size 2.5 on all aspects. These were isolated to the most recent storm snow.
Snowpack Summary
5-40cm of new snow has fallen in the region (5-10 in the north and up to 40 in the central). This new snow is settling and likely being formed into soft wind slabs immediately lee of ridge crests. Moist snowNumerous crusts can be found in the upper 60cm of the snowpack on south facing slopes. The March 15 crust/surface hoar interface is down 50-80cm. Down90-120cm below the surface you may find surface hoar and crusts buried at the beginning of March. This interface is still touchy in some areas, particularly in the north of the region. It also continues to produce sudden planar failures in compression tests.The deeper facet/crust persistent weakness buried at the beginning of February, now down 120 - 200cm, still seems to be reactive and should not be trusted. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive. Weak basal facets exist in many areas, but without a large load, triggering is unlikely.
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.