SAN FRANCISCO — A strong storm was forecast for Northern California, prompting officials to issue flash flood watches for several rural areas hardly hit by last year's wildfires.
El Nino storms lined up over the Pacific started soaking California with light rain Monday but a series of stronger systems are expected to arrive starting Tuesday, forecasters said.
The National Weather Service issued a flash-flood watch for Northern California communities affected by several destructive wildfires last summer and fall.
At least two more storms are expected to follow on Wednesday and Thursday, possibly bringing as much as 3 inches of rain.
As much as 15 inches of rain could fall in the next 16 days in Northern California, with about 2 feet of snow expected in the highest points of the Sierra Nevada, said Johnny Powell, a forecaster with the National Weather Service.
To the south, persistent wet conditions could put some Los Angeles County communities at risk of flash-flooding along with mud and debris flows, especially in wildfire burn areas.
The brewing El Nino system — a warming pattern in the Pacific Ocean that alters weather worldwide — is expected to impact California and the rest of the nation in the coming weeks and months.
El Nino storms in the early 1980s and late 1990s brought about twice as much rain as normal, Jet Propulsion Laboratory climatologist Bill Patzert said. The weather also caused mudslides, flooding and high surf.
In recent weeks, a weather pattern partly linked with El Nino has turned winter upside-down across the nation, bringing spring-like warmth to the Northeast, a risk of tornadoes in the South, and so much snow across the West that even ski slopes have been overwhelmed.
Big parts of the country are basking in above-average temperatures, especially east of the Mississippi River and across the Northern Plains.
In Arizona, El Nino conditions will help push a parade of Pacific Ocean storms inland with light to moderate snow falling in the high country and rain in lower elevations, forecasters said Monday.
The National Weather Service says a series of weather systems will drop snow in the high country and rain in lower elevations as the week progresses.
El Nino's effects on California's drought are difficult to predict, but Patzert said it should bring at least some relief.
Doug Carlson, spokesman for the California Department of Water Resources, pointed out that four years of drought have left California with a water deficit that is too large for one El Nino year to totally overcome.
The record drought in California has forced Gov. Jerry Brown to order cities to conserve water by 25 percent compared to the same period in 2013.
State officials said residents in November missed their 25 percent water conservation mandate for a second month running.
Felicia Marcus, chair of the State Water Resources Control Board, says California remains on course to beat its long-term goal through February. Marcus wouldn't say ahead of Tuesday's formal announcement exactly how much residents fell short of the target.
In Southern California, Residents of the Silverado Canyon burn area in Orange County and the Solimar burn area in Ventura County were told they may want to evacuate in advance of the storm, but have not been ordered to do so.
Los Angeles Mayor Eric Garcetti warned people to clear gutters and anything in their yard that might clog storm drains; assemble an emergency kit; and stockpile sandbags if their home is susceptible to flooding.
An effort also was underway to provide shelter for homeless people.
"We want as little damage and destruction and as little death as possible," Garcetti said.
Between 2 and 3.5 inches of rain is predicted to fall across the coastal and valley areas of Southern California through Friday, with up to 5 inches falling in the mountains.
"This series of storms are definitely associated with the El Niño phenomenon in that the jet stream has taken a fairly significant southward trajectory in the Pacific on its return flow back into the California coastline," said Bob Benjamin, a forecaster with the weather service.
Associated Press writers Christopher Weber in Los Angeles and Paul Davenport in Phoenix contributed to this report.