Regions
Northwest Inland.
Several days of cold benign weather ahead. Concerns include wind slabs at higher elevations and the ongoing potential to trigger deep persistent slabs in shallow snowpack areas.
Confidence
Low - Due to the number of field observations
Weather Forecast
Expect a mix of sun and cloud for the forecast period. Ridgetop winds should remain generally light to moderate from the east with alpine temperatures sitting at about -20.
Avalanche Summary
No new avalanches have been reported in the past few days.
Snowpack Summary
Generally light accumulations of low density snow have occurred in recent days. In some areas wind effect at higher elevations has resulted in wind slabs on east and north aspects. About 25cm below the surface, you may find a variety of old snow surfaces including stiff wind slabs, facets, crusts and surface hoar. The new snow may have a poor bond to these interfaces, especially in places where the slab is stiffer and more cohesive due to winds. At treeline, the average snowpack depths are 120-190 cm and a well consolidated mid-pack of approximately up to 100 cm sits above weak basal facets (sugary snow) near the ground. Recent snowpack testing has shown sudden easy results down 25 cm on a surface hoar layer and sudden hard results down 100 cm within the faceted snow.The deeper basal weakness remain a concern, especially in thin rocky start zones and shallow snowpack locations.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.