Red Flag Warning Issued For Napa, North Bay Mountains

NAPA COUNTY, CA — A fire weather watch issued Tuesday was upgraded to a red flag warning from 11 p.m. Wednesday until 11 a.m. Thursday, the National Weather Service San Francisco Bay Area said.

A shift toward a drier air mass and offshore flow will lead to locally critical fire weather conditions across the interior North Bay Mountains. The areas of greatest concern are locations in Napa County and into interior Sonoma County at or above 1,000 feet including the Vaca and Mayacamas ranges.

"These areas will see the strongest winds, lowest humidity, have the driest fuels, and they received little to no wetting rainfall earlier this week," the weather service said.

Locally gusty north to northeast winds overnight will coincide with poor humidity recoveries. Winds are expected to diminish Thursday, but widespread critically dry humidities — as low as 8 to 15 percent — will prevail throughout the day.

Despite not being the strongest wind gusts observed in an offshore wind event, the combination of these wind gusts and the present dry fuels and minimal humidity recovery overnight, critical fire conditions are expected.

"If a fire is started, rapid fire growth is possible," the weather service said. "Vigilance is encouraged and a reminder to not be that spark."