A brief period of dry weather is expected the next few days with cold mornings and morning fog. Precipitation returns by the end of the week with major mountain travel impacted expected over the weekend. Very difficult travel conditions with likely chain controls and possible road closures. Low visibility due to a combination of wind and heavy snow.
Discussion
Skies have cleared out across most of interior NorCal as the low has moved southeast of the area. Dew points are in the mid to upper 30s across the Central Valley, and with generally light winds, fog is looking more likely than frost. IR difference imagery is already showing a strip of fog developing over the eastern edge of the valley from east of Sacramento southeastward into the San Joaquin Valley. Fog may become more extensive, and locally dense, in this area around sunrise but will lift by mid- morning.
Short-wave ridging today and early Thursday will bring a brief period of dry weather. Clouds will already be increasing tonight and this should help to keep things a bit warmer but still chilly, but will also limit fog potential.
Upper level trough then approach the area Thursday with the trough axis pushing over the far northern part of the area later Thursday into early Friday. Shower chances begin Thursday afternoon in the northern part of the area, then continue to spread south during the evening and overnight. Better forcing will be in northern areas and that is where we can expected the highest QPF with this system.
Snow levels will be lower in the 3000 to 4000 foot range with most of the accumulation above 3500 feet. Generally looking at 5-10″ from I-80 north with some locally higher amounts on the higher peaks.
A Winter Weather Advisory remains in effect. Flow will become more zonal once again on Friday ahead of what will be a stronger more impactful trough for later Friday into Saturday.
We should see a break in precip by the mid-morning Friday into the afternoon. Warm air advection precip will develop late Friday afternoon into the overnight.
Heavier precip is expected on Saturday with the main trough and cold front along with strong southerly winds.
Extended Discussion (Sunday through Wednesday)
Showers Sunday as post-frontal cold upper low moves into interior NorCal. Heavy snow continues in the Sierra Nevada early Sunday as snow levels lower into the upper foothills. Model variations exist with how quickly the low exits the area with lingering showers Monday, mainly over the Sierra Nevada. Models have trended drier through midweek under upper ridging, while NBM continues to bring more precip into the area Wednesday. Below normal high temperatures expected through the extended period.