Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
A westerly flow dominates the next few days. A number of weather systems are lined up to bring varying amounts of precipitation and wind to the interior regions.Friday: Light to locally moderate snowfall, alpine temperatures -7, winds moderate west and southwestSaturday: Moderate to locally heavy snowfall, alpine temperatures -8, winds strong to extreme west and southwest. Freezing level rising to 1200m for a short period in the morning. Sunday Light snowfall, Alpine temperatures -7, moderate west winds.
Avalanche Summary
There are no new reports of avalanche activity in the past 2 days. However I would expect to see an increase in natural and rider/skier triggered avalanches as new snow amounts continue to accumulate and the wind speeds pick up over the next 2-3 days.
Snowpack Summary
Up to 30 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. 70-90cm 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 are variably 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.