Rain returns today with a short break expected tonight and most of Saturday before a stronger system moves through Saturday night and Sunday bringing gusty winds, rain and heavy mountain snow. Dry weather expected through much of next week.
Discussion
Radar shows a band of light to moderate rain beginning to spread into the Sacramento Valley from the coast and Bay Area. Rainfall so far to our west has amounted from 1/4 to 1/2 inch in some areas from the North Bay area northward. All the clouds are resulting in considerably milder temperatures across the region early this morning with the Central Valley seeing current temperatures in the upper 30s to upper 40s, around 5-15 degrees warmer compared to 24 hours ago.
Most of the energy with this incoming system is heading to the north into the PacNW, so the front will weaken as it progresses inland today. QPF of around a third of an inch will be possible in the Sacramento Valley with considerably lighter amounts expected to the south of Sacramento into the northern San Joaquin Valley. Wetter mountain areas will likely see 1/2 to 1 inch.
Snow impacts are expected to be relatively minor in the northern Sierra today with around an inch or two of accumulation possible on Donner Pass and Echo Summit, and perhaps 3-4 inches of accumulation across some of the highways in eastern Shasta and Tehama counties.
A short break in the weather is expected tonight and most of Saturday as a weak short-wave ridge traverses the area. We may see enough clearing this evening for some patchy fog in the valley south of Yuba City by Saturday morning. High clouds in advance of the next system will be increasing late tonight and may disrupt this fog potential.
Timing has sped up a bit with the next system forecast to move in later Saturday afternoon bringing moderate to heavy precipitation as the front moves in on Saturday evening. Gusty southerly winds of 25-35 mph will precede the front across the valley.
Precipitation is forecast to turn more showery late Saturday night and Sunday with the upper trough moving through, and a few thunderstorms will be possible – mainly Sunday afternoon.
Heavy snow will likely continue across the northern Sierra, and we’re still looking at the potential for 18-30 inches of snowfall accumulation over the higher passes through Sunday evening leading to major travel impacts.
Showers end Sunday night and dry weather is forecast to return early next week with seasonably mild days and cool nights. Some patchy late night and morning frost and fog will be possible in the Central Valley.
Extended Discussion (Tuesday through Friday)
Ensembles show ridging building across interior NorCal early next week. This will result in dry conditions and near normal daytime highs. A weak wave brushes to the north by the middle of next week, with increased cloud coverage and perhaps a slight chance of light precipitation across the mountains north of I-80. Ridge rebuilds late next week, with continued dry conditions.
Temperatures through the forecast period will range from the upper 50s to low 60s in the Valley, with 40s and mid 50s over the mountains. Overnight lows are expected to generally range from the mid 30s to upper 30s in the Valley, with areas of Valley frost possible Tuesday morning.