Red Flag Warning Issued For Napa, North Bay Mountains

NAPA COUNTY, CA — The National Weather Service San Francisco Bay Area issued a red flag warning Monday for the mountains and valleys of the North Bay.

A red flag warning means that critical fire weather conditions are either occurring or will shortly. A combination of strong winds, low relative humidity and warm temperatures can contribute to extreme fire behavior.

During the red flag warning period from 11 p.m. Monday through 8 a.m. Wednesday, winds are forecast to become more north-northeasterly and to increase over the highest peaks and ridges to 10 to 25 mph, with gusts generally up to 30-35 mph, and maximum gusts up to 40 mph possible at the highest peaks.

"When the Fire Weather Watch was upgraded to this warning, it was decided to include all of the North Bay Mountains, although the strongest wind gusts are expected to be over Napa and Northeast Sonoma counties," the weather service said.

"These offshore winds will provide critical fire conditions with dry humidity values through the event, and even drier conditions overnight Tuesday and into Wednesday with poorer humidity recovery expected due to less marine layer influence."

According to the weather service, "Bursts of gusty offshore winds and dry conditions will develop tonight and carry into the next several days... .These weather conditions, in combination with very dry fuels, will result in an increased risk of new wildfire starts and rapid wildfire spread."

The first burst will primarily affect the North Bay mountains Monday night through Wednesday morning, according to weather officials.

A lull in the offshore winds is expected from Wednesday morning through Wednesday evening, but drying will continue and carry over into the second burst. The culmination of offshore winds and very dry fuels, along with very dry conditions are possible from Wednesday night through Friday morning and has the potential to impact higher-terrain locations in the North Bay mountains, along with locations in the East Bay hills, the Diablo Range and the Santa Cruz Mountains.