Tricky avalanche conditions exist out there, use a conservative approach and make good choices. Happy Holidays and play safe!
Weather Forecast
By Thursday an upper ridge will build behind the cold front bringing cooler conditions with mostly cloudy skies and light precipitation amounts. Light northwest winds will persist through the forecast period and freezing levels will be at valley bottom. Alpine temperatures will fall to -15.
Avalanche Summary
On Tuesday, reports from the field were still indicating that the buried surface hoar layer is very touchy to skier/ rider triggers and numerous avalanches size 1-2.5 were reported. With a thicker slab overlying this touchy layer, I don't expect things to improve over the holiday period and suspect this layer is primed for human triggers.
Snowpack Summary
New snow 10-30 cm fell Tuesday night, with southern locations seeing the higher amounts. Moderate SW winds accompanied the snowfall adding more load to the upper snowpack. This brings storm snow totals 40-90 cm above a very touchy surface hoar layer that was buried mid-December. Below 2100 m this storm slab sits on a thick, solid crust that has been acting as a perfect sliding layer. Storm slabs will be very touchy to the weight of a skier/ rider, especially in wind effected areas. A hard rain crust with facets from early November is buried over 1 m down and is still reactive to light loads in some locations.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.