Heavy rains bring road closures, flooding to Sonoma County

A multiday storm drenched Sonoma County with subtropical moisture from the Pacific Ocean early Friday, pushing small streams over their banks, flooding some low-lying roadways and causing minor crashes along Highway 101.

By Friday night, the system had produced up to 3 inches of rain in the county’s lowest areas and up to 5 inches in the mountains, said Steve Anderson, a meteorologist with the National Weather Service.

The areas burned by the October wildfires appeared to have held on so far, with no major mudslides or debris flows reported, though a more intense deluge was anticipated overnight.

“So far so good,” said Paul Lowenthal, Santa Rosa’s assistant fire marshal. “We are kind of in a holding pattern now of waiting to see how this shapes up.”

Santa Rosa fire stations boosted staffing levels Friday because of the storm, using an extra engine with three additional firefighters and another battalion chief, Lowenthal said. Officials were less concerned with the expected precipitation totals than the potential rate and intensity of rainfall, which could signal danger in the burn scars if it comes down too hard and fast.

“They’re not forecasting that, but we’re also aware that there’s the potential for it to occur,” Lowenthal said. “We’re definitely preparing for the worst but hoping for the best.”

In anticipation of the potent atmospheric river, the weather service issued a flood watch for the region through this morning. Stream gauges showed some flooding already occurring in south central Sonoma County, prompting a flood advisory for that area - including Rohnert Park, Sebastopol, Graton and parts of Petaluma - until 10 p.m. Friday, according to the weather service.

The storm so far has been “about what we were expecting,” said Anna Schneider, meteorologist with the National Weather Service.

“We’re in a bit of a lull right now, but we are expecting some more precipitation tonight,” she said.

Flooding caused road closures in the west county, including Bodega Highway at Salmon Creek and part of Green Valley Road west of Graton, according to Sonoma County transportation officials.

The storm caused about 10 road closures in the unincorporated areas by late afternoon, according to Johannes Hoevertsz, director of the county’s Transportation and Public Works Department. He described them all as “locations that typically flood.”

The Russian River was set to crest in Guerneville tonight at 26 feet, 6 feet below flood stage.

County officials are patrolling the burned areas this weekend to monitor for troublesome spots and clear fallen trees or branches where necessary, Hoevertsz said.

“It looks like we’re going to be busy this weekend,” he said.

The county was aided by a new network of? 22 rainfall and stream gauges installed in the areas burned in October by the Tubbs and Nuns fires. Many of those gauges had recorded around 2 to 2.5 inches of rainfall by Friday evening, and one gauge by Jack London State Historic Park showed 4.3 inches fell over the prior 24 hours. Data from the gauges are publicly available online at sonoma.onerain.com.

Petaluma police issued a weather advisory for the northern end of the city, specifically focused on Stony Point Road and Petaluma Boulevard North as well as Old Redwood Highway and North McDowell Boulevard. Police said Penngrove Creek was at “a low-lying flood level,” prompting Lt. Ron Klein to warn residents of the potential for flooding through 5 a.m. today.

Mendocino County officials also warned residents the storm could trigger localized slides, debris flows or flooding in some areas burned by the Redwood fire six months ago. Rick Ehlert, the county’s emergency services coordinator, urged residents near the burn zones to “monitor conditions in their area for potential risks to property and life safety.”

Numerous rain-related crashes were reported in Sonoma County throughout the day. CHP Sgt. Josh Kolstad estimated about 30 accidents by Friday afternoon along Highway 101, but no one was seriously injured, he said.

“For the most part, they were solo spinouts or two-vehicle collisions because of the rain,” Kolstad said.

A power outage in the Sonoma Valley affected ?147 Pacific Gas & Electric Co. customers in the Mission Highlands area Friday evening, according to the utility’s website. A spokeswoman said earlier the company had extra crews in seven Bay Area counties, including Sonoma, Marin, Napa and Mendocino, to respond to any weather-related outages.

Schneider expected the heavy rainfall to clear out of the county by early Saturday morning but she said a chance of rain was forecast for Tuesday. She anticipated “off and on wet weather” for the rest of the week, just not as strong as the current storm.

Staff Writer Kevin Fixler contributed to this report. You can reach Staff Writer J.D. Morris at 707-521-5337 or jd.morris@pressdemocrat.com. On Twitter ?@thejdmorris.