Strong Pacific storm moves through Monday into Tuesday with heavy precipitation and strong wind producing flooding and mountain travel impacts. Additional storms move through second half of the week into next weekend.
Discussion
Powerful cold front moved through overnight producing strong wind, heavy precipitation, and isolated thunderstorms. Wind gusts over 60 observed at local airports with 68 mph at KMCC, 64 at KMHR, and 63 at KSMF. As a result widespread reports of downed trees/power lines and power outages. Winds have peaked and will be trending down through the morning.
NCFR developed along main baroclinic zone around 0848z over Central/Southern Sac Valley producing narrow band of intense rainfall. Front and associated precip will continue to push east this morning. Snow levels currently running around 3500 feet in the Shasta mountains and 4500 to 5500 feet in Western Plumas/Northern Sierra Nevada. Additional local snow accumulations up to around a foot possible today. Precip expected to wind down this morning with scattered showers this afternoon, mainly north of I-80.
Focus then turns to next big storms Monday into Tuesday as strong baroclinic zones taps into deep moist 1-1.5 inch PW plume. Widespread moderate to heavy precipitation expected beginning after 06z Mon with first wave along with another round of strong southerly wind.
Snow levels initially forecast around 5000 feet with onset of next system but look to trend upward Monday above 7000 feet. Rising snow levels during heavy precipitation will enhance flooding concerns.
Precip turns showery Monday afternoon into night with fropa as winds trend down. NAM depicting some afternoon instability in the Central Valley for thunderstorm potential, CAPEs up to around 500 J/kg in portions of the Sac Valley, although NBM not picking up on this until Monday evening/night.
Precip and wind ramp up again early Tuesday as next short wave trough moves inland. NBM depicting best potential for thunderstorms Tuesday in Southern Sac Valley into San Joaquin Valley.
Snow levels lower back down to around 4500 feet Tuesday into Tuesday night. Precip values Tuesday look to be less than Monday but still significant. Storm total QPF for Monday and Tuesday’s storms look to be around 2 to 4 inches for the Central Valley with around 3 to 9 inches of liquid precip for the foothills and mountains. Snow totals of 4 to 6 feet possible above 6000 feet.
Urban and small stream flooding will be an issue along with potential mainstem river flooding.
Lingering showers Tuesday night then warm frontal precip spreads back into NorCal Wednesday, mainly N of I-80, as next Pacific storm undergoes cyclogenesis off the West Coast.
Systems progression looks to slow Thursday as it encounters downstream amplifying upper ridge. Precip looks to mainly over northern and western portions of the CWA Thursday.
Extended Discussion (Thursday through Sunday)
Clusters and ensembles indicate a wet southwest flow pattern continuing over NorCal from Thursday into the weekend, keeping unsettled weather in place with daily precip chances. Thursday will see light QPF amounts, mainly over the mountains.
Friday will see moderate precipitation amounts with more significant precip amounts again possible Sat/Sun.