Russian River expected to flood from weekend storm

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North Coast residents are being urged to prepare for a potent winter storm expected to make landfall Saturday even as meteorologists say they need another day to be sure which parts of the Bay Area will bear the brunt of its fury.

Four to five inches of rain is predicted to fall on most North Coast cities, enough to send the Russian River, Napa River and Navarro River over flood stage, and trigger road closures and power outages.

But forecasters caution that even a slight shift northward of the atmospheric river flowing toward the Bay Area could mean significantly higher rainfall totals and local impacts.

“Unfortunately, we really won't know that until we see the whites of its eyes and it makes landfall,” said Brian Garcia, warning coordination meteorologist with the National Weather Service in Monterey.

At the moment, the best models show the system hitting Big Sur and Santa Cruz hardest, with the highest peaks in those areas potentially receiving more than a foot of rain.

But forecasters won't really know for sure until Friday where the most intense areas of moisture will land, Garcia said. That means North Bay residents need to be prepared for local totals to go even higher, triggering more intense flooding and power outages.

“I'm just hoping people are preparing well ahead of time for a worst-case scenario,” Garcia said.

Residents of the Mirabel RV Park and Campground weren't taking any chances.

The owners of the Forestville park have ordered everyone living in the 25 trailers on the property to begin preparations to evacuate, said camp host Lora Meeks. The lowest spot in the campground starts to flood when the river hits 28 feet, and because the river is forecast to rise well above that, everyone must leave, Meeks said.

“We've been doing this for so long, we pretty much know when to leave,” Meeks said.

The Russian River is currently forecast to begin rising sharply at Guerneville around 2 p.m. Saturday and crest at 33.4 feet at 3 p.m. Monday, more than a foot over the 32-foot flood stage. The river should then drop back below flood stage by 1 a.m. Tuesday.

That flood prediction is a change from Wednesday, when the river was forecast to crest several feet below flood stage. The latest forecast shifted the storm track more to the north, resulting in the revision, Garcia said.

That level of flooding, however, is considered moderate and only likely to impact the lowest-lying areas of Guerneville and Monte Rio.

“It doesn't mean that we're going to have thousands of people in shelters,” said Christopher Helgren, Sonoma County's emergency manager.

Nevertheless, Helgren urged people to take precautions. The department encourages all residents to keep 72 hours' worth of essential supplies on hand, including emergency water, food, blankets and lights.

For comparison, the river topped 36 feet in 2014 and 48 feet in 1986 and 1995, the latter two events causing widespread devastation.

The Napa River is forecast to crest just above its 16-foot flood stage in St. Helena at 2 p.m. Sunday, but by the time it gets to Napa, the river is expected to remain 5 feet below its 25-foot flood stage.

The Navarro River was facing the worst flooding, expected to crest at 7 p.m. Sunday at 32.5 feet several miles inland from the coast, or 9.5 feet above flood stage.

Total rainfall expected in Sonoma County ranged from 3.4 inches in Petaluma to 4.8 inches in Cloverdale, with Santa Rosa in between at 3.9 inches. The famously wet Venado, in the hills west of Healdsburg, is expected to receive more than 7 inches.

The predicted totals, if they hold, are not significantly higher than those the county saw in the most recent storm, but the impacts should be greater because the ground is now completely saturated, said Steve Anderson, National Weather Service forecaster. Combined with winds of up to 30 mph, this storm should pack significantly more punch, he said.

“There will be more widespread power outages due to downed trees, more debris on roads, and creeks and rivers will rise much faster than the last storm,” Anderson said.

County road crews were clearing culverts, stabilizing road shoulders and filling potholes in preparation for the storm, said Rob Houweling, manager of the road maintenance division. Over the weekend, they'll be closely watching low-lying roads such as Mark West Station Road, Slusser Road, Healdsburg Trenton Road, Green Valley Road, Valley Ford Freestone Road and Valley Ford Road, closing them when necessary.

For the latest information on closures, go to roadconditions.sonoma-county.org.

For information about where to fill sandbags, visit sonomacounty.ca.gov/Public-Safety/Sandbag-Pickup-Locations.

Fire crews around the county have been reviewing their protocols for water rescues, which have become all too common as drivers find themselves stuck in rain-swollen roads despite clear closure warnings.

“It's amazing how many times I've seen people go past two different barricades and then get stranded in the water,” said Schell Vista Fire Chief Ray Mulas. “I have no idea what they are thinking.”

You can reach Staff Writer Kevin McCallum at 707-521-5207 or kevin.mccallum@pressdemocrat.com. On Twitter @srcitybeat.