Why the next two months are crucial for wildfires in the SF Bay Area

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The worst of the 2022 wildfire season in the San Francisco Bay Area is likely still at least a month away with the fire risk expected to reach its height in September and October, experts said in the latest wildfire outlook for Northern California published by the U.S. Forest Service on Monday.  

This is typical of most years when the risk for wildfires shoots up in early fall as the moisture-rich summer fog subsides and drying offshore winds kick up. Low humidity levels and desiccating winds combined with the dried-out grasses and trees on the ground create ideal conditions for fires to spark and spread.  

“I do expect these off-shore wind events to pick up in frequency and show up more often in late September to October, which is pretty typical for the fall season,” said Brent Wachter, a fire meteorologist at the U.S. Forest Service’s Geographic Coordination Center in Redding, Calif., who helped write the new outlook report. “We don’t know whether or not we’ll see more of these events than usual.”

The National Significant Wildland Fire Potential Outlook released wildfire forecasts for areas across the U.S. 

National Significant Wildland Fire Potential Outlook

Expert analysis by the National Interagency Fire Center released Monday shows that both the East Bay and the North Bay have an above-normal risk for wildfire in September, while the entire region falls in this high-risk category in October. 

A wild card in the forecast is arrival of the rain season in fall. “There’s conflicting signals for how dry or wet the fall will be,” Wachter said.

A factor experts are considering when forecasting coming months is the impact of La Niña. Data that looks at past years marked by La Niña indicate that Northern California could see above normal rain in October, but Wachter said computerized weather models suggest a “significant dry signal.”

The National Significant Wildland Fire Potential Outlook released wildfire forecasts for areas across the U.S. 

The National Significant Wildland Fire Potential Outlook released wildfire forecasts for areas across the U.S. 

National Significant Wildland Fire Potential Outlook

The San Francisco Bay Area has seen an active summer wildfire season with small blazes popping up almost daily, some causing evacuations, in June and July, Wachter said. One person died in a fire in west Sonoma County that tore across 63 acres of dry grass. But June and July have not seen extreme fire behavior in the Bay Area as heavy coastal fog, often pushing inland, has pulled moisture into the region and brought occasional light drizzle.

“If you can punch holes into an extended higher fire danger period, those period of drizzle are going to lessen the threat,” Wachter said. 

Wachter added that the jet stream has also remained active the last two months with several low-pressure systems passing over Northern California, delivering heavy cloud cover and some sprinkles. 


The region has seen a few chances for thunderstorms in July due to the desert Southwest monsoon season and moisture climbing into Northern California. Those chances will persist into the first and second weeks of August before the monsoon season ends.  

In August, the far East Bay has an above-normal risk for wildfires, while the rest of the Bay Area remains in the normal range. 

 

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