Regions
Northwest Inland.
Careful attention to terrain choices are the "words to live by" right now. Buried surface hoar and facets could be triggered with a small avalanche.
Confidence
Fair - Due to the number and quality of field observations
Weather Forecast
Pacific moisture moving through the area for the next few days should bring us 5 to 10 cm of new snow by the end of Tuesday, with a break on Wednesday, then another 5 to 10 cm on Thursday and Friday. Winds from the S-SW, moderate to strong at upper elevations throughout the forecast period. Freezing levels should remain around 500 m, but may spike to 1800m on Wednesday, then return to around 500 m on Friday.
Avalanche Summary
No reports of avalanche activity yesterday.
Snowpack Summary
SW winds are creating wind slabs on lee aspects in exposed terrain, generally depositing snow on N and NE aspects. Below the recent storm snow is a rain crust at lower elevations and a temperature crust that formed on the surface above treeline from the recent temperature inversion. In the mid-pack a surface hoar layer has been reported, although it appears to be spotty in distribution. Near the base of the snowpack is a November crust-facet combination that will hopefully soon no longer be a problem.
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.