New snow and wind will build touchy and reactive storm slabs through the weekend. Conservative terrain choices are crucial.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Saturday
Weather Forecast
The weather pattern has finally shifted as a surface low moves onto the Coast bringing new snow through the weekend. Saturday: Snow amounts 10-20 cm with light- gusting strong southwest winds. Alpine temperatures near -8 and freezing levels 700 m. Sunday: Snow amounts 5-10 cm with strong southwest winds. Alpine temperatures -10.Monday: Trace of new snow with ridgetop winds light from the southwest. Alpine temperatures near -3.
Avalanche Summary
No new avalanches were reported on Thursday. New reactive storm slabs will build through the weekend.
Snowpack Summary
New snow has buried a wide variety of old snow surfaces including stiff wind slab or wind effected snow at upper elevations, sun crust on steep southerly slopes, surface hoar and surface facets in sheltered locations. The mid-January interface (facets) is buried approximately 60-100 cm down and recent snowpack tests have shown hard, yet sudden planar results. A total of 60-120 cm of settled storm snow now forms the upper snowpack and is generally bonded to a crust below. The exception may be thin rocky areas that host deeper weaknesses. The mid and lower snowpack are generally well settled, but still feature a number of facet and crust layers that are currently dormant but require monitoring with significant change.
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.