Don't bother washing your car today.
The National Weather Service is forecasting a series of Pacific storms will move into the Central Valley starting Sunday and last through next weekend.
The storms will translate to much-needed snow in the Sierra Nevada and, eventually, the runoff that fills foothill reservoirs that furnish the valley's main water supply.
"We are expecting several storms to roll through the area in the next week to 10 days," said Kate Hora, spokeswoman for the Modesto Irrigation District. "The weather forecasters are also saying we could get a healthy amount of snow above 5,000 feet. Although everyone focuses on rainfall, what we're concerned about is snow."
Sacramento meteorologist Johnnie Powell said the rain
will start late Sunday, then continue in waves consistently about every 12 hours.
"So at this rate we shouldn't go 24 hours without rain starting in the next week," he said. "It's going to be moderate rain, occasionally heavy. It's considered a wet pattern."
He said the Central Valley can expect as much as 6 inches over the next week. While he said he didn't expect any individual storms to break daily rainfall records, it should be steady and consistent.
That would be welcome news in Modesto, where the 4.37 inches of rain received this winter is nearly a full inch less than the average.
The storms have even larger implications for the state. Many experts agree that the predicted rain might help fill California's reservoirs, which have been depleted by a three-year drought.
The key will be where the rain and snow falls throughout the state.
El Niño, the weather-influencing trend in the Pacific Ocean, often brings more snow to the southern Sierra than the northern part of the range. But the state's largest reservoirs — Shasta and Oroville — are in the north.
The two reservoirs need 110 percent of average runoff this year if they are to provide the normal supply of water for millions of Southern Californians, millions of acres of San Joaquin Valley farmland and a faltering ecosystem in the Sacramento-San Joaquin Delta.
The area's reservoirs are all below capacity to varying degrees.
Don Pedro Reservoir on the Tuolumne River, whose users are largely in the Modesto and Turlock irrigation districts, is at 71 percent. New Melones on the Stanislaus River is at 49 percent and Lake McClure on the Merced River is at 40 percent.
About half the rainfall season is already over, and the snowpack — a rough predictor of later runoff — is only about 75 percent of average in the northern Sierra.
But state and federal officials know meteorologists are talking about a sudden turnaround.
"I'm optimistic," said Maurice Roos, hydrologist for the state Department of Water Resources. "One typical winter storm will bring the snowpack up pretty close to average. Of course, we need more than one winter storm."
For valley residents, the rain's most immediate impact will be lots of soggy shoes and dripping umbrellas.
Powell said there will be some wind, up to 35 mph from the southeast, as each front arrives. But mostly the storms will just dump water on the valley.
She said if the storm fronts come in one after another, some localized flooding could be expected because the ground will not have had enough time to absorb the previous moisture.
But Hora said flood control levels have not been reached on the Don Pedro Reservoir, so there should be "more than enough capacity to hold runoff."
"Take it easy and allow yourself extra time (to get where you're going)," she said. "It's going to be wet."
Fresno Bee reporter Mark Grossi contributed to this report.
Bee staff writer Marijke Rowland can be reached at firstname.lastname@example.org or 578-2284.