Regions
Northwest Inland.
Conditions vary significantly within the region from South to North. Avalanche danger could be slightly lower than indicated in the northern half of the region due to less recent snowfall.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Synopsis: We should see a brief lull in the weather on Monday before the arrival of another strong frontal system late in the day. There could be a few breaks Monday morning followed by increasing cloud and snow in the evening. Overnight Monday and through Tuesday we could see 10-20 cm of snow. Winds increase once again to strong from the S-SW. The freezing level stays at valley bottom on Monday and Tuesday with treeline temperatures around -10 to -15. Snow and winds should gradually taper off on Wednesday. An above freezing layer might also form near 2000 m.
Avalanche Summary
There are a couple recent reports of natural and rider triggered wind slabs up to size 1.5 from steep treeline features. These wind slabs have involved only the resent storm snow. Touchy wind slabs should continue to build in lee terrain over the next couple days.
Snowpack Summary
Recent winds have been highly variable with strong W-NW winds followed immediately by strong SE-NE winds. Hard and soft wind slabs should be expected on a variety of slopes in open terrain. rain was reported to almost 2000 m on New Years Day in the southern part of the region. Since then there's been around 20-50 cm of new snow. The new snow may be resting on older wind slabs or surface hoar in northern areas. Down 40-70 cm you may find another surface hoar layer, although it appears to be spotty in distribution. Near the bottom of the snowpack is a crust facet combo that was buried in mid-November. This layer is currently dormant and produces variable results in snowpack tests. I suspect it will remain sensitive to new inputs in the form of new snow and wind for the foreseeable future.
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.