Significant accumulations of new snow are expected on Wednesday and Thursday. If winds are strong, the avalanche Danger may be HIGH.
Confidence
Moderate - Wind speed and direction is uncertain on Thursday
Weather Forecast
Wednesday Night: 15-30cm of new snow / Moderate southwest winds / Freezing level at 800mThursday: 5-10cm of new snow / Moderate southwest winds / Freezing level at 1000mFriday: 20-30cm of new snow / Light southwest winds / Freezing level at 1300mSaturday: Light flurries / Light and variable winds / Freezing level at 2000m
Avalanche Summary
Areas that experienced recent heavy rain should see the snowpack quickly stabilize as temperatures cool. With that said, new snow that accumulates on this refrozen surface may form unstable new storm slabs before the new snow has a chance to form a solid bond. High alpine areas that haven't seen rain are on a different trajectory. Here, recently formed storm slabs will need more time to stabilize as they experience continued loading from new snow and wind.Looking forward, new snow and wind on Wednesday night is expected to promote a new round of storm slab activity in higher elevation lee terrain.
Snowpack Summary
Heavy rainfall soaked the upper snowpack at most elevations over Sunday night and Monday. High alpine elevations in areas like Sky Pilot and the Chehalis Range may have seen thick new storm slabs develop over the same time period. Below these elevation-dependant surface conditions, storm snow totals from the past week reached 110-180 cm. The crust that exists beneath these recent snow accumulations is likely to have now formed a solid bond to the overlying snow.
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.
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.