Regions
Northwest Coastal.
Strong winds and new storm snow are driving the danger ratings. Fresh and reactive slab will likely build through the forecast period.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Wednesday: Snow accumulations 5-10 cm with moderate-strong SW winds. Alpine temperatures high of -6.Thursday: Snow 10-20 cm with strong SW winds. Alpine high of -3 and freezing levels 600 m. Friday: Mostly cloudy with possible sunny breaks. Snow amounts 5-10 cm and light-moderate ridgetop winds from the SW.
Avalanche Summary
On Monday, several natural wind slab avalanches were reported up to size 1 above 1300 m. A cornice also failed size 2 and did not pull a slab avalanche from the slope below. Changing wind directions and new storm snow will likely develop new wind slabs at upper elevations.
Snowpack Summary
Recent storm snow 10-20 cm has fallen and buried a new surface hoar layer. Im uncertain of how well preserved this layer is and if it is widespread. The new snow has also buried a variety of old surface conditions including isolated wind slabs, sun crusts, and facetted snow. At lower elevations (below 1000 m) a supportive rain crust exists. Deeper in the snowpack 30-60 cm down a layer of surface hoar was buried on February 10th at tree line elevations and continues to be reactive in some recent snowpack tests. Below this layer, the snowpack is generally settled and strong. The exception is shallow snowpack areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern.
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.