The powerful storm that has already drenched the North Coast sent ashore a third wave Saturday night that was expected to trigger flooding of creeks and rivers throughout the region over the next two days.
Up to 7 inches of rain was predicted for upland areas starting about 7 p.m. through Sunday afternoon, with up to 4.5 inches predicted for the flatlands, according to the National Weather Service.
Emergency officials were scrambling Saturday to prepare for the storm's latest onslaught as residents lined up at hardware stores and elsewhere in search of emergency supplies.
High winds were expected to compound the mess, falling trees and power lines and causing road closures and power outages.
Many of region's largest waterways, including the Russian, Petaluma, Napa, and Navarro rivers, were expected to reach flood stage, if not spill their banks.
The Russian River was forecast to meet flood stage in at least two spots: near Hopland in Mendocino County at about noon Sunday and in Guerneville at about 7 a.m. Monday
The projected crest in Hopland could be just over the 21-foot flood stage. Based on past floods, water could cover secondary roads, including stretches of Highway 222 and Highway 175, plus low-lying structures in the Hopland area, according to the National Weather Service.
Hopland Fire Chief John Bartlett said his department was readying boats to aid in rescues of stranded residents. Many of those in the area have been through worse, he said. But he urged those in need of emergency help to stay put and call 911.
"We'll go and get them," he said.
In Guerneville, the river's crest was forecast to be at the 32-foot flood stage. Affected areas could include Lower Mill Street in Guerneville, Old Bohemian Highway in Monte Rio and a number of other riverside roads, resorts and campgrounds.
Emergency officials were evacuating many of those campgrounds Saturday.
"They're predicting those are going to be under water," said Chris Helgren, Sonoma County's Emergency Services manager.
Helgren said his office expected moderate flooding in the lowest areas of downtown Guerneville.
At the True Value Hardware store in town, customers were stocking up on batteries, lamp fuel, flashlights and firewood, said Nick Millar, the general manager.
"It's not too chaotic yet," he said.
Stockpiled sand was available throughout the region, with free pickup spots at many fire stations or county yards.
Mendocino County Sheriff's Sgt. Shannon Barney, who oversees emergency services, said county public safety departments would be on alert early Sunday, when floodwaters are expected to swell on the upper Russian River.
Road crews and shelter staff also will be available to deal with flooded roadways and housing issues, he said.
"We're geared to set up wherever we need to, depending on what areas get affected worst," Barney said.
Downstream, the surge of runoff is set to crest in Healdsburg about 2? feet below flood stage at 6 p.m. Sunday.
Sonoma County officials said they would be activating an emergency command post this morning to coordinate the response along the river and around the rest of the county.
In Petaluma, fire officials said they anticipated flooding along tributaries of the Petaluma River. That could happen as early at 5 a.m. Sunday, when the tidal waterway is set to reach high tide, Petaluma Fire Battalion Chief Jeff Holden said.
The Napa River also was expected to flood near St. Helena and Napa at about noon Sunday.
The Navarro River in Mendocino County, already 6 feet over flood stage along the coast, was set to rise an additional 4 feet by Sunday afternoon.
The wet weather will be accompanied by strong winds, prompting a patchwork of wind advisories and warnings stretching from the Santa Cruz Mountains to the Oregon border.
Gusts of up to 50 mph are forecast in higher-elevation areas of Sonoma and Napa counties and parts of Marin County. In Mendocino County, parts of Lake County and much of the northern coast, the gusts could reach 60 mph, with sustained winds of 25mph, according to the weather service.
The heaviest rain was expected from 10 p.m. Saturday through mid-morning Sunday, with showers tapering off by the afternoon, said Austin Cross, a National Weather Service meteorologist.
Monday is expected to be mostly dry in the region. A weaker front, carrying not much more than an inch of rain for the wettest areas, is forecast for Tuesday.
Already, about 10 to 12 inches have fallen across much of the North Coast, with wetter areas getting well over a foot of rain, the weather service said.
More extensive localized flooding is expected Sunday and Monday along urban creeks and roadways. Officials urged residents to exercise caution around standing and moving water.
"The basic message is stay away" from those water bodies, said Sonoma County Supervisor Efren Carrillo. He said he spent much of Saturday touring his west county district, seeing the aftermath of the previous two storm fronts and supervising preparations for the current one.
He called it an "all-hands-on deck moment" for emergency responders. The fewer rescues required, the more those hands can help out others in need, Carrillo said.
"It's an important message," he said. "Don't travel if you don't have to."
You can reach Staff Writer Brett Wilkison at 521-5295 or brett.wilkison@pressdemocrat.com.
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