Strong solar radiation on Tuesday will likely trigger newly formed storm slabs and loose wet avalanches, especially in southern parts of the region. Be conservative in terrain selection and watch for changing conditions throughout the day.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
On Tuesday, conditions will remain sunny and dry. A weak front will move onto the coast bringing generally light precipitation to Interior regions later Tuesday night. Ridgetop winds will blow light-moderate from the E-SE. Freezing levels will range from 1500-1800 m. Wednesday will see mainly cloudy skies with light convective precipitation which will continue through mid-day. Ridgetop winds will be light from the NW and freezing levels near 1700 m. Later Thursday, a strong front will approach the Coast and start to move inland bringing precipitation amounts to the Interior regions anywhere from 2-10 mm. Ridgetop winds will be strong from the SW and freezing levels will hover around 2000 m.
Avalanche Summary
On Sunday, reports of numerous size 1-3 natural slab avalanches and skier remote avalanches have been observed. Many of these larger events started as wind and storm slab avalanches from upper elevations. These avalanches have occurred on a variety of aspects with northerly aspects being most reactive. These have initiated from 2000-2800 m in elevation. With forecast sunshine and solar radiation, touchy slab avalanches are expected in the alpine and loose wet sluffing is possible from steep solar slopes at all elevations. 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, 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. In the alpine, strong winds during the storm are redistributing the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. 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 but now have the potential to wake-up with the current warm temperatures and new loading. A basal weakness has recently become active with the warm conditions and several avalanches have released to the ground.
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.