Fed by two days of near-constant rain, the Napa River is expected to top its banks in some low-lying areas by Thursday morning, with water flowing for the first time in two years into the Oxbow Commons bypass.
Parts of the Napa Valley had received three and four inches of rain by Wednesday afternoon, with another couple of inches expected to fall overnight on saturated soil.
The California Highway Patrol responded to a dozen incidents of road flooding, mud slides, fallen trees and vehicles off the road Wednesday, but no major injuries were reported. Some 70 customers in east Napa and in St. Helena briefly lost power when branches fell across electrical lines, Pacific Gas & Electric reported.
The National Weather Service issued a flood warning Wednesday morning for Napa County’s small streams and creeks, saying the flood threat would grow with the additional rain forecast through Thursday morning.
The Napa County Flood Control District planned to close the flood gates at Oxbow Commons at 5 p.m. Wednesday as a safety precaution as the river continues to rise.
“The bypass is probably going to flow, probably at about 6 a.m.,” Rick Thomasser, flood control operations manager for the county, said Wednesday afternoon.
“This is shaping up to be a similar-size event to what happened in the winter of 2016-17,” when the bypass carried water twice, Thomasser said.
Based on the forecast, Thomasser said there should be no serious flooding in the city of Napa. Overflow culverts should keep Napa Creek in its banks downtown, he said.
The Town of Yountville sent an alert Wednesday afternoon to notify residents that the powerful storm expected overnight would cause flooding at Yountmill Road and Oak Circle at Heather Street, according to the alert.
The city of Napa and the flood district were to have crews on hand all night Wednesday monitoring likely areas where runoff could cause a problem, Thomasser said. Some of the Upvalley crossroads may flood before waters recede Thursday afternoon, he said.
“It’s going to be a wet night,” Thomasser said Wednesday, adding “We’re certainly used to this size event.”
As of 3 p.m. Wednesday, the rain gauge at the city’s Corporation Yard on Jackson Street had recorded 1.06 inches since Tuesday evening. Elsewhere, Mount Veeder received 1.65 inches, Mount George 2.4 inches, Angwin 3.44 inches, Hopper Creek in Yountville, 2.05 inches and Sulphur Creek at Pope Street in St. Helena 2.96 inches.
The city of Napa has set up a sandbag station at Memorial Stadium, 1340 Menlo Ave. There is no charge for sandbags and sand.
The highest wind gust in the area so far was recorded on Mount St. Helena, a 75 mph blast at 1:50 a.m. Wednesday.
Things should start drying out by Thursday afternoon when rain turns to showers. The forecast for Friday through the weekend is for “chance of showers.”