Update Oct. 13: The National Weather Service (NWS) issued another red flag warning Thursday night for much of the Bay Area, although it won’t go into effect until 5 p.m. Friday. It will last through 11 p.m. Saturday.
Northerly winds will decrease through much of Friday, although local gusts up to 25 mph are still possible on higher ridges and peaks. North to northeast winds are then forecast to increase once again late Friday and become locally strong and gusty Friday night and Saturday.
Strongest winds are expected to be at elevations above 1,500 feet in the North Bay Mountains and East Bay hills on Friday night and Saturday morning. Winds are forecast to decrease by late Saturday.
The range of the fire threat is not as broad as the previous warning, mostly concentrated in the East Bay from the Oakland Hills down to Fremont, as well as eastern portions of San Jose and Santa Cruz, but not Monterey or San Mateo County.
The scope of the warning also extends north to cover parts of Napa, Santa Rosa, and Marin. Note that the forecast calls for the strongest winds to blow in generally northerly directions from San Francisco, toward existing fires.
[Update: No, scratch that. Turns out that in this case a northerly wind means that it’s blowing from the north, potentially pushing North Bay fires closer to the East Bay.]
While red flag warnings are in effect, the U.S. Forest Service advises against—and, in areas where it has sufficient jurisdiction, bars—activities such as campfires and other means of outdoor cooking; use of torches or other tools that produce open flame; smoking; or “operating an internal combustion engine,” although obviously many commuters have little choice on the latter point.
Wednesday night the National Weather Service (NWS) issued a red flag warning covering the East Bay Hills, San Jose, Monterey, and most of San Mateo County, as strong winds threaten to add to Northern California’s fire crisis.
A red flag is an NWS tool that indicates imminent fire danger. Although like everything else when it comes to predicting the weather, it’s hard to tell whether increased risk will translate to actual fire, people in the affected area should take these warnings seriously.
A red flag warning is issued for weather events which may result in extreme fire behavior that will occur within 24 hours. [...] A Red Flag Warning is the highest alert. During these times extreme caution is urged by all residents, because a simple spark can cause a major wildfire.
NWS says the warning will remain in effect until 5 p.m. Thursday. The weather agency cautions that “any fires that develop could spread rapidly” and warns against outdoor burning of any kind
The warning is in effect for any area “above 1,000 feet in the San Francisco Bay Area” and at similar elevations in San Benito and Monterey counties.
It’s the troublesome winds that engender this new danger, as the most recent forecast calls for gusts up to 50 MPH in most of the affected region:
Low humidity and gusty northerly winds will combine with dry fuels to produce critical fire weather conditions, especially across higher elevations of the North Bay Mountains, East Bay Hills, Santa Cruz Mountains, the Santa Lucia Mountains, and the mountains of San Benito County and Interior Monterey County.
Another round of very dry conditions and gusty offshore winds will arrive late Friday though early Saturday for the North Bay Mountains and Diablo Range.
Friday and Saturday will see a Fire Weather Watch throughout the region, a similar warning one step below red flag in severity.
- Fire Warning Bay Area [NWS]
- Red Flag Warnings [Cal Fire]
- Wind, Fire Hazards [NWS]
- California North Bay wildfires: What we know so far [Curbed SF]