Regions
Northwest Coastal.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Synopsis: A brief ridge of high pressure builds in for Monday bringing drier conditions and a mix of sun and cloud. The next system is forecast to affect the region on Tuesday. Monday: A mix of sun and cloud. The freezing level is around 600 m. Winds are light from the northwest.Tuesday: Light to moderate snowfall – 10-15 cm. The freezing level is around 500 m and winds increase to moderate or strong from the south-southeast. Wednesday: Unsettled with flurries or periods of snow. The freezing level is steady near 500 m and winds remain moderate from the south.
Avalanche Summary
Observations are still quite limited due to poor weather but there are a few reports of natural slab avalanches up to size 3 from treeline areas, and numerous reports of loose moist avalanches up to size 2 from steep below treeline terrain.
Snowpack Summary
The snow continues to pile up with another 25-40 cm overnight. This brings the total storm snow amounts from the past week to well over 1 m. Mild temperatures have promoted rapid settlement of the storm snow. This new snow fell on a crust, old wind slab, and/or surface hoar depending on aspect and elevation. One recent snowpack test near Shames resulted in a hard "pops" shear on the buried surface hoar, down around 60 cm at the time. Most areas are reporting that the snow has bonded well to the underlying melt-freeze crust. Cornices that now loom over many features may become weak with continued growth and/or daytime warming. The mid and lower snowpack layers are generally well settled and strong.
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.