Lingering rain and snow showers today with dry weather Friday and Saturday. Cold nights Thursday night through Saturday night. Rain and snow chances return for the second half of the weekend with unsettled weather continuing next week.
Discussion
The upper level trough that has brought a wet 12 to 18 hours to NorCal is begining to push into the northern part of the state with its associated cold front sitting just to the south of Sacramento to Blue Canyon. Widespread rain and snow continue ahead of the cold front with more showery precip behind it. The widespread activity will continue to push to the south with the front and will clear the area by daybreak.
Light showers will linger though into the early afternoon as the trough axis pushes east through the area. The best chances will be during the morning hours and over the higher elevations. Snow levels are currently 1000-2000 feet over Shasta County and 2500-3500 feet over the Sierra. Overall these snow levels will stay steady overnight and will start to come up after daybreak. An inch to several inches of additional snow accumulation will be possible between now and daybreak with the highest snow accumulation from Highway 50 south.
Upper level riding then builds in for Friday and Saturday. This will bring quiet conditions with clearing skies. Fog will likely become an issue across the valley as the substance inversion strengths. Friday evening into Saturday morning looks to be the best chances for fog.
Cold air will build in behind the departing system and that will bring chilly daytime highs along with frosty nights and mornings. Upper level ridging will be pushing to the east on Sunday as troughing begins to build over the west.
A weak short wave will push into the PacNW Sunday pushing a cold front into far northern CA. This will bring the chance for a few light showers mainly over the mountains north of I-80. Rain and snow accumulation look to remain light.
Extended Discussion (Monday through Thursday)
Deep troughing will be building over the west for the extended period and that will bring unsettled weather to NorCal. Ensembles are in great agreement on troughing over the west but do differ when it comes to details. Some want to keep the long wave trough a bit further to the west while some want to keep digging it south.
Either way we will likely see good chances for rain and snow during the extended period with southern areas favored to see higher rain and snow totals. Details on exact waves of precip and totals will become more clear as we get closer.