North Coast drenching proved a jarring shift away from drought-mentality mode (w/video)

The largest winter storm in years walloped the North Coast on Thursday, delivering more rain than local creeks could hold, flooding roadways, prompting widespread school closures and disrupting life for most of the region.

With rainfall of at least 4 inches in most areas - and more than double that in the wettest locations - the outright drenching proved a jarring shift away from drought-mentality mode, forcing residents to rethink normal daily activities, reschedule meetings and exams, and cancel what would have been festive holiday events.

Fields, streets and parking lots laid bare a day earlier became lakes that allowed the rare adventurer to kayak where cars normally would dominate, notably in downtown Healdsburg, where merchants scrambled to barricade doors and windows against the flood caused when Foss Creek overflowed.

Thoroughfares were closed by floodwaters and fallen trees and power was cut at one point to more than 19,000 households and businesses.

Driving anywhere invoked risk.

More than three dozen county roads were closed Thursday evening due to flooding, slides and downed trees, according to Rob Silva, Sonoma County’s road maintenance division manager.

Two Petaluma homes were damaged earlier in the day when gusting morning winds knocked over trees, one on Sunnyslope Avenue and the other on D Street near El Rose Drive, city fire personnel said.

The lower Russian River was still rising Thursday night, expected to reach flood stage of 32 feet early Friday morning in Guerneville and to crest around 34.7 feet at noon, according to the National Oceanic and Atmospheric Administration.

Sonoma County emergency personnel said they issued voluntary evacuation notifications to 278 households in low-lying areas of Monte Rio and Guerneville that faced potential impacts from flooding, either because of roadway flooding or inundation of property.

It wasn’t clear how many had heeded or would heed the recommendation, though there were no reports of evacuated residents at emergency shelters, county spokeswoman Rebecca Wachsberg said.

“Based on past history - most of the people there have been through this many times - so we don’t anticipate that many people will choose to evacuate,” she said.

The county’s emergency operations center was to remain staffed overnight and Friday to monitor developments and take further action if needed, she said.

A similar watch-and-wait scenario was playing out late Thursday in Petaluma, where the Petaluma River, swelled by high tide in the afternoon, spilled over its banks on the north end of town, inundating streets already affected by creek flooding around the auto mall and Leisure Lake Mobile Home Park, emergency personnel said.

The mobile home park remained cut off from the rest of the town, though everyone had power and phone service and was being monitored, Petaluma Fire Capt. and Acting Battalion Chief Jude Prokop said.

The deluge also isolated people in and around Industrial Avenue and the auto mall, requiring a half-dozen evacuations, Prokop said. But many business owners and personnel chose to stay put to protect commercial interests, he said.

There were also two swift-water rescues necessitated when motorists drove past barricades into flooded areas, Prokop said.

With runoff still draining into the Petaluma basin, it was hard to say when roads would clear, he said, though it was hoped flooding would subside overnight.

The powerful storm, which arrived Wednesday night, dumped more than 6 inches of rain in Guerneville in the 24-hour period ending at 4 p.m., the National Weather Service said.

Santa Rosa got 5.13 inches; Healdsburg, 5.91; Sebastopol, 4.6 inches, and Petaluma, 3.16, the weather service said.

The wet spots were Cazadero, with 8.76 inches; Venado, west of Healdsburg, with 8.56 inches; and Rio Nido, with 8.3.

The heaviest band of rainfall went through Sonoma County before midday Thursday, moving at a good clip so that fears it might stall overhead and drop even more precipitation weren’t realized. That fate was reserved for Napa and Marin counties, where the storm stayed for prolonged periods, National Weather Service meteorologist Steve Anderson said.

The morning rainfall nonetheless turned creeks into rushing torrents, overwhelmed local roads and prompted last-minute closures of dozens of schools around the area. Others had announced Wednesday that they would not be in session. Most schools around Sonoma County are to remain closed Friday.

Despite a high number of calls that kept fire crews and others racing through the day, some emergency personnel said the wind, though high, was not as fierce as anticipated, accounting for fewer downed trees and power lines than might have occurred.

“What saved us is we haven’t gotten a whole lot of wind,” Monte Rio Fire Chief Steve Baxman said. “But we sure have a whole lot of water.”

Santa Rosa Fire Battalion Chief Jack Piccinini said, “It hardly stands up against any really serious storms that we’ve seen over the years. It’s just that no one’s used to it because we haven’t had any real storms in the last three or four years.”

The storm’s relatively short stay in the county Thursday meant most rivers would not be receiving the maximum runoff expected, reducing expectations for flooding.

Where the lower Russian River had been predicted at various points to reach almost 6 feet above flood stage, or nearly 38 feet, the Thursday night forecast put the peak level closer to 2½ feet above flood stage, averting what Sonoma County Emergency Manager Christopher Helgren said was probably hundreds of evacuations that now won’t be necessary.

“Once you start to get above the 35 (foot level), then that exponentially raises that number,” he said. The lesser forecast “made a big difference for us,” he said.?The storm still left a mess in its wake, including road closures and about 5,500 PG&E customers still without power Thursday night. The largest disruption affected 846 households and businesses in Sebastopol, though most of the 130 other power failures involved far fewer people, mostly in west Sonoma County communities like Forestville, Guerneville and Occidental, as well as Petaluma, PG&E personnel said.

Company spokesman J.D. Guidi said Sonoma and Humboldt counties bore the brunt of the storm in terms of power failures, and said some would linger because of flooding and other access issues despite plans to have crews work through the night to make repairs.

Road maintenance manager Silva said county road crews, likewise, would continue working until at least midnight to clear county roads.

They had been focused, particularly, on Porter Creek and Mark West Spring roads, major access routes that had been flooded in numerous locations because of rocks that slid off embankments on the uphill side and plugged drainage culverts, causing runoff to overwhelm the road.

Many other roads remained flooded or blocked by debris would be restored to use relatively quickly in most places, though those closer to the Russian River and affected by its flooding - such as Wohler and Slusser roads, for example - might remain inaccessible longer, he said.

You can reach Staff Writer Mary Callahan at 521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB. Staff Writers Randi Rossmann, Matt Brown and Jamie Hansen contributed to this story.