New snow and wind will likely build fresh and reactive wind slabs at upper elevations on leeward slopes.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The cold arctic outflow will reside as an active weather pattern reaches the Coast tomorrow bringing slightly warmer temperatures, strong winds and new snow at higher elevations.Friday: Snow amounts 5-10 cm with ridgetop winds light-moderate from the southeast. Alpine temperatures near 0 degrees and freezing levels rising to 800 m.Saturday: Snow amounts 10-20 cm with ridgetop winds light-gusting strong from the southwest. Alpine temperatures near 0 degrees and freezing levels near 700 m.Sunday: Heavy precipitation expected to be a mix of snow and rain. Ridetop winds light-gusting strong from the southwest and freezing levels rising to 100 m.
Avalanche Summary
No recent avalanche observations have been reported on Thursday. Reactive wind slabs at higher elevations will be the primary concern and loose dry sluffing from steeper terrain features are likely. The new snow will have a poor bond to the old snow surfaces and firm crust.
Snowpack Summary
10-20 cm of new snow is expected to fall over the region today. This new storm snow will likely have a poor bond to the old snow surfaces which consist of a firm crust and hard wind press. The mid and lower snowpack are settled and well bonded with the average snowpack depth up to 300 cm at treeline.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.