First storm of the week moves out, stronger system arrives tonight

March 26, 2019 – Light precipitation continues today, mainly over the mountains. A stronger Pacific storm moves in tonight and Wednesday with afternoon thunderstorms possible on Wednesday.

Unsettled weather will continue on Thursday with scattered showers before the return to dry weather for Friday into the weekend.

Discussion

Radar continues to show a rather narrow, north to south oriented, area of precipitation across NorCal associated with the slow moving frontal zone. The heaviest precipitation overnight has continued to be over eastern Butte and western Plumas Counties where 1-2 inches of rain has fallen the past 12 hours.

Only slight movement of the precipitation to the southeast is expected today as the large upper low off the coast begins to pivot closer. Snow levels will remain rather high today, around 5500-6500 feet, so travel impacts will be limited to the higher passes where another 4-8 inches of snowfall accumulation will be possible into this evening.

The next system is forecast to move into the region later tonight and Wednesday will likely be more impactful with heavier mountain snow and thunderstorms for the Central Valley. Warm-advection will lead to more widespread precipitation by later this evening as the next system approaches.

At this time, it looks like the cold front will sweep across interior NorCal on Wednesday morning setting the stage for an active afternoon of post-frontal showers and thunderstorms. Snow levels will lower to 4000-5000 feet by Wednesday evening, and to 3500-4500 feet on Thursday. 2-3 feet of snowfall accumulation will be possible along the northern Sierra crest, with 3-6 inches down to around 4000 feet, by Thursday afternoon.

Improving weather conditions are expected for most of the area on Friday as the trough shifts east. A few showers may linger across the northern mountains.

Extended Discussion (Saturday through Tuesday)

Drier weather expected over the weekend as upper level ridging moves through interior NorCal. Models diverge with solutions early next week, but main theme appears to be unsettled weather as a series of short wave troughs move through the CWA beginning Sunday night into Monday and continuing through Tuesday.