Periods of rain, snow, and breezy winds through Wednesday with flooding concerns and mountain travel impacts. Additional storms expected late this week and weekend. Gusty southerly winds today will bring downed trees and power outages.
Discussion
The break in the weather late Monday and overnight is rapidly coming to an end as a strong negative-tilt mid/upper trough approaches. Satellite has been showing a band of thunderstorms approaching the coast overnight, and radar is now showing this initial line approaching the coast from about Pt Reyes south. Hi– res models continue to show this line moving inland into the Central Valley around 12Z with the strongest segment from about Yuba City southward into the northern San Joaquin Valley.
Heavy rain, lightning and strong winds will accompany the line as it moves through early this morning. A brief tornado or two cannot be ruled out, especially south of Sacramento where low-level shear is maximized.
The post-frontal airmass will remain unstable through the day supporting scattered showers and thunderstorms with accumulating small hail becoming the primary threat, though enough shear remains for a non-zero threat for funnel clouds or a brief weak tornado.
Besides the severe weather threat, heavy snow will increase in the mountains today and continue through much of the night with significant travel impacts likely to develop this morning. Will extend the Winter Storm Warning into early Wednesday.
Tightening surface gradient will also support breezy to windy conditions through much of the day, and a Wind Advisory will go into effect early this morning. Much of the valley will see another break tonight while snow persists in the mountains, then another wave of precipitation (mainly lighter) will move in on Wednesday.
Precipitation is forecast to retreat northward later Wednesday with may areas likely to see dry weather Thursday into Friday before the next system moves in. The Shasta County mountains and north end of the Sacramento Valley will be the exception as southerly orographic flow continues the chance of precipitation for that area.
Extended Discussion (Saturday through Tuesday)
Models show another system moving through over the weekend with widespread moderate to locally heavy precipitation Saturday with showers Saturday night into Sunday.
Additional waves keep wet windy weather into early next week, but model differences result in some forecast uncertainty with timing and amount of precip at this time.