April 14, 2018 – Dry and warmer weather today, then Pacific storm moves through Sunday and Monday with rain, mountain snow, and gusty wind. Dry Tuesday then possible unsettled weather Wednesday and Thursday.
Discussion (Today through Tuesday)
Upper ridging will result in dry and warmer weather today with above normal temperatures. Highs forecast in the mid to upper 70s for the Central Valley with upper 50s to lower 70s for the mountains and foothills.
Higher clouds spread over the forecast area this evening as heights lower and Pacific frontal system approaches. Models begin spreading frontal precip across far NW portions of the CWA Sunday morning. Pressure gradients also increase over Interior NorCal at that time, ahead of approaching baroclinic zone. Model precip spreads to about I-80 by 00z Monday. Winds increase in the Central Valley with guidance suggesting potential for wind advisory speeds generally from around Oroville northward Sunday afternoon. Precip turns showery in the Central Valley after 00z Mon as heavier precip spreads into the Western Plumas mountains and Sierra Nevada. Snow levels Sunday evening initially start out around 4500 to 6500 feet.
Precip decreases in the Western Plumas mountains aft 06z Mon and in the Sierra after 12z. Snow levels Monday morning expected to be around 3000 feet. Showers continue Monday with best chances in the Central Valley during the afternoon. Models also showing increased instability during this time as cold upper trough moves through. Potential for thunderstorms exist Monday in the Central Valley and foothills. Shear profiles suggest potential for isolated rotating storms but more unidirectional and thus main threat appears to be small hail with colder mid level air moving through. Precip winds down Monday evening with drier weather Tuesday. Attm storm total QPF looks to be up to around half an inch in the Central Valley, locally higher with stronger convective storms. Liquid totals in the foothills and mountains of up to around 1.25 inches are forecast, with snow totals of 6 to 12 inches above 5000 feet.
Extended discussion (Wednesday through Saturday)
Uncertainty continues next week in how quickly the cold closed low will move onshore the West Coast. Appears main shower chances will be Wednesday and Thursday with gradually drier and milder weather late in the week. This is not expected to be a particularly cold or wet system with less than a quarter inch of QPF and only a few inches of snow possible above 4500-5000 feet.