A strong Pacific storm will move through today bringing moderate to heavy precipitation and renewed flooding concerns along with strong wind and thunderstorms. Showers Sunday then another weatker storm for Monday for mainly the southern half of the forecast area. Drier weather Tuesday into Wednesday then a weak system Wednesday into Thursday. Dry weather returns late week.
Discussion
Today has been an active day as a powerful Pacific storm system with a strong moisture tap has brought moderate to heavy rain, gusty winds and thunderstorms. The heaviest precipitation occurred morning through early afternoon as a strong cold front moved through.
This morning several Narrow Cold Frontal Rainbands (NCFRs) brought brief periods of heavy rain, lightning, small hail and strong, gusty winds. These linear storms created local flooding, brought down powerlines, and created very heavy snow with whiteout conditions as they tracked into the mountains. These lines extended north to south, from around Redding to Sacramento. Scattered showers and isolated thunderstorms have developed in instability behind the front, though cloud cover is limiting CAPE. Some of these storms have shown some rotation on radar, with strong shear environment behind the front.
There is the potential for strong gusty winds, small hail, and potential funnel clouds with any thunderstorms that develop. Convective activity should end around 6-7 pm this evening.
A Flood Advisory continues into this evening, the Flood Watch continues through Sunday morning, with river and stream rises continuing even as rainfall intensity diminishes.
The heavy snow showers (2 to 4 inches an hour at peak) and along with winds gusting 40 to 60 mph brought near zero visibility. This resulted in the closure of area highways including I-80 from Colfax to the Nevada State line. Highway 20 was also closed, as well as a section of Highway 49.
Snowfall will remain moderate to heavy through around 10 pm, with lighter snow continuing through Sunday.
Another system arrives Sunday into Monday, but this storms looks weaker, with heaviest snow south of I-80 as the storm takes a more southerly track.
A Winter Storm Warning continues until 10 pm Monday night.
Gusty winds developed today, especially along the lines of thunderstorms. Gusts 40-50 mph were recorded today. Now that the cold front has moved through, winds are breezy but lighter. This will gradually decrease tonight. The Wind Advisory has been cancelled.
Gusty southerly winds will develop over the northern San Joaquin Valley Sunday night, with gusts 30 to 40 mph possible there.
Showers end Monday night into Tuesday morning, then drier weather expected Tuesday into early Wednesday as upper ridge moves inland. Models suggest next Pacific storm will spread precip in from the NW after 18z Wednesday through Thursday morning, however at this time, this system looks to be trending drier and should be much weaker than recent storms.
Extended Discussion (Wednesday through Saturday)
Another Pacific storm modeled to track across interior NorCal Wednesday into Thursday. System appears to weaken as it spreads precip into the forecast area after 18z Wed through early Thursday.
Drier weather then returns Friday into the weekend as models finally reestablish EPAC high off the West Coast.