Confidence
Fair - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
As the low off the Oregon coast moves inland and South, light-moderate snowfall amounts are expected through Thursday. The low deteriorates by Friday morning and is being replaced by a ridge, bringing dry and sunny conditions with very little wind. Overnight into Thursday: Light-moderate snow accumulations. Ridgetop winds will blow light from the West. Alpine temperatures near -7 and freezing levels at 1500 m.Friday and Saturday: Ridgetop winds will remain light from the West. Alpine temperatures near -4 and freezing levels rising to 1600 m in the afternoon then falling to valley bottom overnight.
Avalanche Summary
Natural loose dry sluffing from steeper terrain, especially where the crust exists.
Snowpack Summary
Up to 40 cm of storm snow fell last weekend. Storm slabs exist on all aspects and elevations and are touchy, especially on slopes lee of the wind. Cornices have grown large on ridgelines and may act as a trigger on slopes below. Loose dry avalanches are likely, especially from steeper slopes and terrain features.Below 1900 m a crust has formed and may act as a sliding layer for the new snow. Below the crust the snowpack is moist. Mid and lower snowpack layers are generally well settled.
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 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.
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.