First Autumn Rain, Heavier Than Expected, a Boon for Firefighters

A NASA satellite image of smoke from the North Bay fires on Oct. 9, 2017. (NASA Worldview )

Update, 7:45 a.m. Friday, Oct. 20: A quick look at rainfall totals across the Bay Area shows we got a little more out of our first storm of the season than forecasts suggested. The highest total in the nine counties: .90 of an inch at the Middle Peak weather station on Mount Tamalpais.

Much of the countryside swept by fire last week in Napa and Sonoma counties got a half-inch of rain — which should prove a big help to firefighters completing containment of the vast blazes.

Next up: a round of clear, warm weather with temperatures in the 80s in much of the region by Monday; parts of the Santa Clara Valley could reach the lows 90s.

A list of your 46 favorite reporting stations, by way of the National Weather Service’s California-Nevada River Forecast Center, is below. Totals are for the 24 hours ending at 6 a.m. Friday.


Original post, Wednesday, Oct. 18: Last October — almost exactly a year ago, in fact — the Bay Area got its first rain of the season. The farthest reaches of the North Bay, especially, got a good soaking from a storm that had started out on the other side of the Pacific as a typhoon.

The rain signaled the end of the 2016 fire season in that part of the state.

Forecasters say we’ll see our first autumn rain later this week. Weather models project a rather modest storm, sweeping down from the Gulf of Alaska. The wettest Bay Area locations, again in the far North Bay, are expected to get maybe a third of an inch of precipitation. Less is forecast as you go south, with areas in the South Bay forecast to receive just a few hundredths of an inch.

But context is everything. Last year, we were just hoping that we’d see something like a normal, rainy winter. (We got our wish and then some.)

This year, we’re looking forward to the rain, even if it’s just an anemic little storm, to help douse the catastrophic fires that have overrun huge swaths of the North Bay.

Will the expected storm be useful in helping tamp down the fires? Does it signal an end to the fire season?

The answer to the first question: A little, perhaps, but not too much. To the second: Definitely not.

Craig Clements, an assistant professor of meteorology at San Jose State and director of the school’s Fire Weather Research Laboratory, said in an interview with KQED’s Craig Miller this week that the rain’s impact depends on the kinds of fuels — or vegetation — involved.

Clements said the grasses so common in California’s hills are known as “one-hour fuels,” meaning they respond nearly immediately to moisture or to heating and drying.

“It can rain, and then in an hour, they can burn again,” Clements said.

The brush and bushes that thrive in California’s long rainless season are dry after nearly six months with little moisture, and they take longer to respond to rains, Clements said.

“The shrubs take about 25 days for the rain in the soil to get to the stems and such,” Clements said.

Bottom line, though, even this minor episode of wet weather will aid firefighters in the North Bay.

“This may not shut down everything immediately, but it will definitely help the fires burning currently,” he said.

After the rain, forecasters say we’ll see a return to warm, sunny weather, with highs reaching the mid-80s in the North Bay by Tuesday. Temperatures will be even hotter in Southern California, which is also famously vulnerable to autumn severe fire weather.

So when will we see the end of fire season? It’s still anyone’s guess.

First Autumn Rain, Heavier Than Expected, a Boon for Firefighters 20 October,2017Dan Brekke

Author

Dan Brekke

Dan Brekke is a blogger, reporter and editor for KQED News, responsible for online breaking news coverage of topics ranging from California water issues to the Bay Area’s transportation challenges. In a newsroom career that began in Chicago in 1972, Dan has worked as a city and foreign/national editor for The San Francisco Examiner, editor at Wired News, deputy editor at Wired magazine, managing editor at TechTV as well as for several Web startups.

Since joining KQED in 2007, Dan has reported, edited and produced both radio and online features and breaking news pieces. He has shared in two Society of Professional Journalists Norcal Excellence in Journalism awards — for his 2012 reporting on a KQED Science series on water and power in California, and in 2014, for KQED’s comprehensive reporting on the south Napa earthquake.

In addition to his 44 years of on-the-job education, Dan is a lifelong student of history and is still pursuing an undergraduate degree.

Email Dan at: dbrekke@kqed.org

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