Regions
Northwest Inland.
Pay close attention to new snow amounts and whether or not the surface snow is loose or cohesive. Tricky conditions are likely if a cohesive slab forms.
Confidence
Low - Due to the number of field observations
Weather Forecast
Saturday: Cloudy with a chance of flurries. The freezing level is at valley bottom and winds ease to light. Sunday: Mainly cloudy. The freezing level is at valley bottom and winds are moderate from the southeast. Monday: Cloudy with light snow. The freezing level could rise to 600-800 m and winds increase to strong from the S-SE.
Avalanche Summary
There are very few observations from the region. No new natural avalanches have been reported. One size 1 skier-triggered avalanche was reported on Thursday. This occurred on a relatively small, shallow slope below treeline.
Snowpack Summary
An additional 5-10 cm of snow with moderate or strong southeast winds may be enough to form fresh, reactive wind slabs in lee features. In some places this could also activate buried surface hoar in the upper snowpack, generally found between 30 and 60 cm deep. Stay tuned to signs of instability like recent avalanches, whumpfing, and shooting cracks. The mid pack that was reported to be well settled may have now facetted in the shallower areas, and the deeper basal layers are almost certainly facetted and weak. We have not heard of any full depth releases on weak basal layers yet.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.