Recently formed slabs remain sensitive to human triggering at higher elevations. Solar radiation and its destabilizing effect on the snowpack remains possible even if skies are cloudy.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Wednesday
Weather Forecast
The dry conditions and sunny skies are coming to an end as a series of pacific frontal systems hit the coast and bring cloudy skies and precipitation though the weekend. Wednesday will be fairly dry with a mix of sun and cloud. Ridgetop winds will be light-moderate from the West and freezing levels hover around 1800 m. Thursday will bring light snow amounts near 10 cm. Ridgetop winds will blow strong from the SW and freezing levels 1600-1800 m. Friday will remain cloudy with light precipitation 5-10 mm, and freezing levels rising to 2100 m.
Avalanche Summary
On Monday, reports of numerous size 1-2.5 natural slab avalanches and skier triggered avalanches have been observed. These avalanches have occurred on a variety of aspects with northerly aspects being most reactive. These have initiated from 2000-2600 m in elevation. A couple of these slab avalanches were triggered remotely from 50 m away an there is a still a concern for avalanches to step down to deeply buried weak layers resulting in larger persistent slab avalanches.
Snowpack Summary
At higher elevations, up to 20 cm of new snow sits over a plethora of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs which may still be reactive to rider triggering. Rain has soaked the upper snowpack to around treeline elevation forming a spring-like, melt-freeze crust. In the alpine, strong winds have redistributed the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30 cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. This interface has not been as reactive in the South like it has in the North; however, it still exists and should remain on your radar. The late-Jan crust/surface hoar layer (around 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.