Sunday night's forecast snowfall amounts are uncertain. Pay close attention to how much snow falls (and how hard the wind blows) as wind slabs are the primary concern.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Sunday
Weather Forecast
A frontal wave will move over the South Coast, and track eastward just south of the boarder. This pattern is forecast to bring generally light snowfall to the region by Monday morning. Light snowfall is expected to continue throughout Monday night and into Tuesday morning. By Tuesday afternoon, a drying trend will develop and carry into Wednesday. Remnant arctic air will keep freezing levels at valley bottom; however, an inversion is likely on Wednesday with above-freezing alpine temperatures. Ridgetop winds should remain mainly westerly until Wednesday. They are forecast to hit extreme values on Sunday night and Monday morning, and then remain mainly moderate to strong for the rest of the forecast period.
Avalanche Summary
No new avalanches have been reported, although I suspect there was some wind slab activity in response to Friday's wind event. I expect another round of wind slab activity with new snow and wind forecast for Sunday night.
Snowpack Summary
Snow surfaces are variable with northerly, wind exposed aspects showing firm wind pressing, or a scoured exposed crust. More sheltered locations have up to 30 cm of low density, faceted snow. In the alpine and at treeline, strong northerly winds have transported this snow into stiff wind slabs on opposite slopes. Up to 70 cm below the surface you will likely find a hard, thick crust which formed mid-December. At higher elevations this crust has facets (sugary) snow above it and well-preserved surface hoar up to 10 mm in size in sheltered locations at treeline and below. Where the crust exists, it may be bridging triggers from penetrating to deeper persistent weaknesses. However, on high alpine slopes above where the rain crust formed, or in areas where rain didn't occur, deeply buried facets may still be susceptible to triggering, especially in thinner snowpack areas.
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.