Much-needed rain expected to begin tonight, last through Saturday

After the fourth-driest December on record, Sacramento should see steady precipitation throughout the first half of January.

A half to a full inch of rain is projected between Wednesday night and Saturday morning throughout the Sacramento Valley, National Weather Service meteorologist Craig Shoemaker said. Future showers are anticipated through Jan. 19, though Shoemaker said they remain too far out for him to accurately predict the total downpour.

The first in the series of weather systems is forecast to bring light rain to the Sacramento area by late in the Wednesday evening commute.

The next system hits early Friday morning and carries over into Saturday.

The storms won’t have much impact in the mountains, where 1 to 2 inches of snow is expected around 6,000-7,000 feet Friday and Saturday. The northern Sierra’s eight-station index has been dusted with 12.6 inches of precipitation so far this season, down about 6 inches from the year-to-date average.

A Coastal Flood Advisory has been issued around Eureka, where strong southern winds are expected to steepen waves. Up to an inch of rain is expected in the North Coast as well as the Bay Area, and up to a half-inch in Stockton and Modesto.

Sacramento saw just 0.13 inches of rain in December, the last of which came on Dec. 20, following above-average precipitation in November. The monthly average is 3.9 inches. Every major California city has been significantly drier than average since the “water year” began Oct. 1, which experts believe may have contributed to long-lasting wildfires in the state’s southern half.

A particularly persistent atmospheric barrier known around NWS offices as the “Ridiculously Resilient Ridge” has been shoving rainfall up into Canada over the last month. The two systems expected to impact Northern California this week – one originating in the eastern Pacific Ocean beginning Wednesday, the other coming from the Gulf of Alaska on Thursday night – should help flatten the ridge and push it out over the Rockies, Shoemaker said.

“It’s not unusual that we have (a ridge) in winter,” Shoemaker said. “What is unusual is to have one that persists for such a long amount of time.”

Benjy Egel: 916-321-1052, @BenjyEgel