A heavy snow fall (up to 70 cm) has overloaded a weak snowpack. Stay clear of avalanche terrain. Slopes that have not avalanched are ripe for human triggering.
Weather Forecast
The snowfall tapers off tonight & winds should also drop off slightly. For Saturday, there is a break in the weather with cloudy skies & cooler temperatures expected. A minor front crosses the region on Sunday bringing light flurries & higher winds. Beware - any additional load from wind transport may trigger slopes that have not yet avalanched.
Snowpack Summary
Up to 70 cm of storm snow with moderate to strong WSW wind has overloaded the persistent weak layers. In thicker snow pack areas, the Dec. 10th weak layer of facets & depth hoar is now down 100-150 m with a stronger snowpack below. In thin snowpack areas, the Dec.10th layer is mixed in with the basal facets and October crust.
Avalanche Summary
Over the past 24 hours, there has been a avalanche cycle up to size 3.5, some ran full path, and many have scrubbed to ground. Many steeper features at treeline & below have also avalanched. The natural activity should taper, but slopes will remain hair trigger with any further wind loading or by visitors on or near a slope.
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.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.