Regions
Northwest Coastal.
Outflow winds may have developed new wind slabs at all elevations. New wind slabs may be sitting on a weak layer of surface hoar or sun crust that can act as an easy sliding layer.
Confidence
Moderate - Wind effect is extremely variable
Weather Forecast
On Friday the region will see mainly sunny skies and light ridgetop winds, although areas closer to the coast may see strong outflow winds. Saturday will bring mainly overcast skies, up to 5cm of new snow and strong southwest winds as a Pacific front brushes up along the North Coast. On Sunday, expect a mix of sun and cloud and reduced winds. Freezing levels are expect to remain at valley bottom for all 3 days.
Avalanche Summary
Some recent natural wind slab activity to size 2.0 was reported from the north of the region near the coast where the outflow winds were reported to be strong. There have been no reports of avalanches from the ski operations in the south or from MIN reports.
Snowpack Summary
Snowpack surfaces are highly variable. A melt-freeze crust can be found at or near the surface on steep, solar aspects in the alpine. On most other slopes, 25-40 cm of snow from the Boxing Day storm continues to settle and facet, and new surface hoar has been reported although its distribution is likely variable due to strong outflow winds. In areas where recent winds have been light, shaded slopes will likely provide settled powder. In areas where winds have been stronger, reactive wind slabs may exist, especially in areas where the the slab overlies surface hoar buried by the Boxing Day storm. Professionals in the region are still tracking a few other surface hoar layers that developed throughout December which are now buried in the top 100cm. These layers have likely gained significant strength, and represent a low probability / higher consequence scenario at treeline and below treeline elevations. In colder and shallower snowpack areas watch for weak basal facets.
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.