‘Use Tuesday for preparation’ before atmospheric river hits North Bay

North Bay residents should spend Tuesday getting ready for another round of heavy rain and fierce winds set to barrel into the region Wednesday, with rivers set to surge toward flood stage, topple more trees and make a mess of local roads, according to the National Weather Service.

This atmospheric river, the third to hit the Bay Area since Dec. 26, could drop as much as 8 inches of precipitation over a 48-hour period,on some of Sonoma County’s wettest areas, according to meteorologist Ryan Walbrun, with the weather service’s office in Monterey.

The storm is expected to deposit about 2 to 4 inches of rainfall on the Sonoma County valleys, 4 to 6 inches on the northwest hills and 6 to 8 inches near Cazadero.

Sustained 20-30 mph winds out of the south are forecast, with gusts up to 50 mph and 60 mph above 1,000 feet. At the coast, gusts could hit 70 mph, the National Weather Service said.

“Use Tuesday for preparation,” Walbrun said. “Put a plan in action ahead of time, just in case.”

A flood watch has been issued for much of the state, and a high wind warning is set to take effect at 4 a.m. Wednesday and last until 10 a.m. Thursday morning for most of the Bay Area.

“This is truly a brutal system that we are looking at and needs to be taken seriously,” weather officials said in the report.

Residents living in areas with a higher risk of flooding or mudslides, such as the Glass Fire burn scar, should take some time to craft a plan in anticipation of the storm, according to the Santa Rosa Fire Department.

“Residents should prepare, especially those living in or around the Glass Fire burn scar or areas prone to flooding,” fire officials advised in a Facebook post. “Also, we encourage residents to use (Tuesday) to clear their gutters and storm drains.”

As the heaviest rain sweeps into the North Bay Wednesday night through Thursday morning, so too will wind gusts of up to 60 mph, Walbrun said.

The combination will bring more-hazardous conditions to Sonoma County than what developed during the New Year’s Eve storm, which began in the southern portion of the county and moved south.

The upper Russian River is set to crest at 17 feet Thursday morning in Hopland, where flood stage is 15 feet. The lower river is set to peak at its 32-flood stage in Guerneville on Friday morning.

Last weekend’s storm knocked over trees, flooded the intersection of highways 12 and 121 near Sonoma Friday afternoon and saturated the soils, leaving the North Bay little time to dry out before Wednesday’s storm.

Widespread soft showers started sprinkling intermittently across the North Bay Monday afternoon. This light rain is expected to stop Monday evening, leaving one dry day before the soaking rain.

Monday’s rainy conditions began to subside around 5 p.m. By that point, 0.36 inches of precipitation had been recorded at Charles M. Schulz–Sonoma County Airport, according to the National Weather Service.

Healdsburg was the wettest Sonoma County city with 0.51 inches of rain, followed by Rohnert Park with 0.48 inches and Sebastopol with 0.42. Windsor had 0.39 inches, Santa Rosa had 0.33 inches and Petaluma got 0.24 inches.

In western Sonoma County, Cazadero had 0.52 inches of rain while Occidental got 0.40 inches.

While there were no significant reports of flooding across the region Monday, the rain still added to the ground moisture, increasing the potential for rock or mudslides when the stronger storm hits, Walbrun said.

“It’s not hurting anything right now,” he said of Monday’s rain. “But it’s not going to help.”

This week, Sonoma County and surrounding counties will be at their highest risk for flooding, mudslides and downed trees and downed power lines. Rain rates could reach 1 inch per hour, which is enough to trigger debris flow around the Glass Fire burn scar, Walbrun said.

“With a front of this magnitude, it is conceivable,” he added.

Multiple creeks and streams, including Mark West Creek, are expected to overflow during the heavier rains, Walbrun said.

The rain is expected to end by Thursday afternoon, Walbrun said.

After a 24-hour break, a weaker but still strong storm will begin Friday night and fill the already swelled rivers even more, Walbrun said.

This wet weather pattern is expected to extend into the second week of January, added Brooke Bingaman, another meteorologist at the Monterey office.

Staff Writer Colin Atagi contributed to this report.

You can reach Staff Writer Madison Smalstig at madison.smalstig@pressdemocrat.com. On Twitter @madi.smals.