A Red Flag Warning has been issued for the Bay Area starting Thursday, and yes, San Francisco is included.
A Red Flag Warning has been issued for the Bay Area starting Thursday, and yes, San Francisco is included.:- As expected after Monday’s Fire Weather Watch, the National Weather Service issued a Red Flag Warning for most of the Bay Area, including San Francisco, starting Thursday night.
Wildfires are likely with the Diablo winds and extra-low humidity. Monday’s Fire Weather Watch runs from 11 am Thursday to Saturday night, and now the National Weather Service has issued a Red Flag Warning for the same area starting at 11 pm Thursday.
This comprises much of the Bay Area save the Marin Headlands and sections of Marin and Sonoma County shoreline. The warning lasts until 5 pm Saturday, when winds should calm.
The Monterey County and Big Sur coast are in the danger zone, but the Santa Cruz Mountains and coastal Santa Cruz County are outside.
Fire risk is rising, as the weather service predicts higher winds and 10% humidity. According to forecasters, wind gusts of 30 to 40 mph as of Monday may reach 45 mph,
With isolated gusts of 65 mph along the highest ridgelines in Napa and Sonoma counties. “Stay vigilant!” says the weather service.
San Francisco is rarely warned due to our peninsula location, which protects us from most offshore winds.
The latest warning says we’ll experience the odd Diablo winds blowing east to west starting Thursday night. While the city does not have dry fuels like less inhabited sections of the Bay Area, strong winds might quickly spread a small fire, which could be deadly in a densely populated area.
The weather service advises against starting outdoor fires and driving over dry grasses or foliage, which can start flames.
In October, Diablo winds caused some of the Bay Area’s worst wildfires, SFist reported yesterday. Diablo winds, the NorCal version of Santa Ana winds, are explained here.
In summary, a high pressure system in the Great Basin in Nevada and Utah will push warm air over the Sierra Nevada, into the dry Sacramento Valley, and up and over the Bay Area’s ridge lines,
Compressing and warming it and lowering humidity as it rushes over the highest elevations and down to sea level.
