Recent snowfall amounts vary considerably from north to south. Danger ratings could be slightly higher in the Cascades where the bulk of the precipitation fell on Sunday.
Confidence
Fair - Due to limited field observations
Weather Forecast
Synopsis: The Cascades could see another 10-15 cm by Monday morning. A brief ridge of high pressure will result in drier conditions and sunny breaks on Monday. The next system arrives sometime on Tuesday bringing moderate precipitation through Wednesday. Monday: Cloudy with sunny breaks. The daytime freezing level rises to around 1500 m. Winds are light from the northwest. Tuesday: Increasing cloud with precipitation developing in the afternoon (~10-15 cm). The freezing level is around 1300-1500 m. Winds increase to moderate or strong from the southwest. Wednesday: Moderate precipitation continues. The freezing level is steady between 1300 and 1500 m.
Avalanche Summary
There are no new reports of avalanches from the region. Watch for an increase in solar related avalanche activity on Monday (loose wet, cornice) and the potential for triggering fresh wind slabs in lee alpine terrain.
Snowpack Summary
Recent snowfall amounts vary depending on location and elevation. Some alpine areas (above 1800-1900 m) could have accumulations of over 40 cm from the past couple days. New dense wind slabs are likely in exposed lee and cross-loaded terrain in the alpine. Most of the recent precipitation has fallen as rain below treeline. Rain had turned to snow down to 1000 m on Sunday morning leaving 10-20 cm of moist snow bonding well to wet grains below. Below the dusting of new snow the upper snowpack at lower elevations has become isothermal from recent warm temperatures and rain. Cornices are very large and could pop off with continued mild temperatures.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.