Photo: David Paul Morris / Special To The Chronicle Photo: Santiago Mejia / The Chronicle Photo: Santiago Mejia / The Chronicle Photo: David Paul Morris / Special To The Chronicle Photo: David Paul Morris / Special To The Chronicle Photo: David Paul Morris / Special To The Chronicle

Bay Area weather officials were bracing for an atmospheric river hailing from Hawaii to douse the North Bay and move steadily south by Wednesday morning to bring strong winds, heavy rain and widespread flooding to the region.

The downpour “will be pretty steady” until Thursday and is expected to drop at least 2½ inches of precipitation on most parts of the Bay Area, said Anna Schneider, a meteorologist with the National Weather Service.

The heaviest amount of rain was expected to arrive Wednesday morning, just in time for the early commute.

“We are expecting flooding from this pretty much everywhere,” Schneider said.

Up to 3 inches of rain was expected in Half Moon Bay and 5 inches in Santa Rosa and San Rafael, while some parts of the North Bay mountains could receive up to 8 inches of rain.

“Those are the isolated, rugged terrain,” said Scott Rowe, a meteorologist with the National Weather Service.

A flash flood watch is in effect for the entire region from 10 p.m. Tuesday to 10 a.m. Thursday. In addition to flooding, the storm will bring rapid rises on flood-prone creeks, streams and rivers, which could result in landslides.

Forecasts have the Russian River in Guerneville rising to 33.5 feet, Rowe said. The river’s flood stage is at 32 feet.

In the South Bay, Alameda Creek has the potential to flood, with early forecasts showing the creek rising to 6.2 feet. The flood stage is 6 feet, Rowe said.

Napa River could teeter on the crest of flooding with the water rising to 24.3 feet, and flood stage is 25 feet.

“These weather forecasts are subject to change based on the precipitation throughout the river basin,” Rowe said.

The atmospheric river is also expected to bring strong winds to the region, and a wind advisory and high wind warning is in effect from 10 p.m. Tuesday until 10 a.m. Thursday.

Southerly winds up to 35 mph are expected with gusts up to 60 mph along the coast and on hills above 1,000 feet elevation.

The strong winds could down trees and power lines, officials warned.

On the positive side, the precipitation could bring many Bay Area cities to normal rainfall totals for this time of year, Schneider said.

San Jose is currently at 99 percent of normal for the water year with 9.27 inches of rain, Schneider said. The normal amount of rainfall is 9.39 inches of rain.

San Francisco is about 90 percent of normal with 13.72 inches of rain, just short of the average 15 inches.

Oakland, so far, has received 10.84 inches of rain to reach 86 percent of normal. The standard is 12.66 inches.

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani