Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A westerly flow dominates the next 3 days. A number of weather systems are lined up to bring varying amounts of precipitation and wind to the interior regions.Thursday: Light snowfall, alpine temperatures -7, moderate west winds.Friday: Light snowfall, alpine temperatures -5, winds moderate west and southwestSaturday: Moderate to locally heavy snowfall, alpine temperatures -4, freezing level 1300m, winds moderate to strong west.
Avalanche Summary
There are no new reports of avalanche activity in the past 2 days. Although I would expect that with some new snow combined with moderate winds Wednesday into Thursday that we'll see thin wind slab releases to size 1 in the alpine.
Snowpack Summary
Up to 10 cm of new snow sits on a variety of snow surfaces ranging from older stiff wind slab, a soft layer of facetted snow and/or surface hoar. 50-80cm below the surface from you may find at various depths a thin melt freeze crust below 2100m and a couple of buried weak layers (surface hoar, facetted snow, and/or a crust) that continue to be reactive in snowpack tests.There are two deeper layers of note. The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas and is now buried 90-160cm below the surface. The October deep persistent weak layer consists of a layer of facets sitting on a crust at the base of the snowpack. This layer is predominantly found on northerly aspects at treeline and in the alpine. The depth of both these layers makes directly triggering an avalanche on them unlikely (maybe a heavy load on a thin spot in steep terrain). Their presence could, however, increase the size of a potential avalanche through step-down.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.