Reactive storm slabs are the main concern as stormy weather continues.
Be mindful that deep instabilities are present and have produced recent large avalanches.
There are indications of a destructive, persistent slab problem waking up in the Cascades. Forecasted new snow and wind will likely increase its sensitivity and destructive potential.
Moderate snowfalls and high southwest winds will form reactive storm slabs. Expect hazard to increase with elevation and to be greatest in leeward terrain.
Numerous wet loose avalanches (up to size 2.5) were reported near Yak Peak on Sunday due to rapid warming. A natural size 3 persistent slab was observed in Allison Pass on Saturday. It occurred on a 37°, northeast-facing slope at treeline (1740m) and had a 240 m-wide crown fracture. Storm loading will increase the concern for this type of avalanche activity.
20 cm of new snow overnight overlies 20 cm of moist snow in the upper snowpack. A weak layer of faceted snow or surface hoar is now buried 50 to 60 cm deep and present in higher elevations, particularly shaded terrain.
Storm loading has woken this layer up decisively in neighboring regions and produced a troubling size 3 avalanche in Allison Pass on Saturday. High-elevation rain brought moisture to the facet layer at treeline on Saturday, both a possible trigger and a suggestion that the layer may strengthen soon.
A crust from December exists buried 100 to 150 cm deep, with facets around it in shallow areas. Otherwise, the lower snowpack is strong. At lower elevations, the snow is wet, heavy and water-saturated.
Monday Night
Cloudy with 5 to 10 cm of snow. 30 to 40 km/h south ridgetop wind. Treeline temperature stable around -2°C. Freezing level around 1200 m.
Tuesday
Cloudy with 15 to 20 cm of new snow. 30 to 40 km/h south ridgetop wind. Treeline temperature stable around -2°C. Freezing level around 1200 m.
Wednesday
Partly cloudy with isolated flurries. 20 km/h south ridgetop wind. Treeline temperature stable around +6°C. Freezing level rising to 2700 m.
Thursday
5 to 10 cm of wet snow or rain. 50 to 70 km/h southwesterly ridgetop wind. Treeline temperature 0°C. Freezing level lowering to 1500 m.
More details can be found in the Mountain Weather Forecast.
