Fire season is winding down as rain and snow make their way in

A cold front is expected to bring showers to the Bay Area today

It’s the kind of forecast that Northern California, weary from historic wildfires, has been waiting months to hear.

A cold front moving through the Bay Area will bring widespread rain today, with an inch or more expected in the North Bay Hills and Santa Cruz Mountains, and a quarter inch or so in most Bay Area cities.

Substantial snow also is forecast for the Sierra Nevada from Lake Tahoe north, with 2 to 3 feet forecast at higher elevations by Wednesday.

“This is a good sign,” said Craig Clements, director of San Jose State University’s Fire Weather Research Lab. “We’re ending fire season. We’re going into our winter season.”

The rain will increase soil moisture, not only wetting down the landscape across millions of acres that have been very dry in recent months, but also prompting new green grasses and other plants to begin sprouting, Clements said.

Generally speaking, after an area gets about an inch of rain in the fall, fire season is usually all but over, he added. If no more rain fell in December or January, which is rare, that could dry things out and increase risk somewhat, but still not to the levels California suffered through this summer with 100-plus degree temperatures and strong winds.

“If we had very warm weather you could still get a fire,” he said. “Is it going to be as severe as this summer? No. It’s not going to burn as hot. The air is not as dry. Temperatures are cooler. The soil moisture is higher.”

Farther north, 2 to 4 inches of rain is forecast near Redding and communities closer to the Oregon border. In recent days, Cal Fire officials have allowed burning of dead vegetation and agricultural debris again in Butte, Mendocino, Trinity, Shasta and other Northern California counties.

On Monday, the U. S. Forest Service’s daily fire danger map showed low risk of wildfires for most of Northern California, including the Bay Area. But high risk remained in much of Southern California, particularly around Santa Barbara and Ventura counties.

“The rain will improve our situation. It helps,” said Cal Fire Capt. Issac Sanchez. “But what we want to see is a line of storms — steady precipitation.”

Daniel Swain, a climate scientist at UCLA, noted that research is showing a trend toward drier autumns in California, which is causing a longer fire season most years. This week’s storm system could make a significant difference, he said Monday.

“This will be fire season- ending rain in some areas, including portions of Bay Area,” Swain said in a post on Twitter.

As is often the case with California storms, the weather is coming from the north. A cold storm front is making its way toward California from the Gulf of Alaska, said National Weather Service meteorologist Matt Mehle.

The entire Bay Area region and areas of the Central Coast all are expected to see precipitation. At least three- quarters of an inch and possibly as much as 1 1/2 inches of rain are expected to fall in the Santa Cruz and North Bay mountains.

Forecasters do not anticipate that such heavy rain will cause flooding or mudslides in areas that have been burned by fires this summer.

“We believe this will be a good, solid beneficial rain,” Mehle said. “It does not look to be rain that will add to the debris from the fires or the threat of mudslides.”

In lower- lying areas, such as San Jose and Santa Clara in the South Bay and Concord and Oakland in the East Bay, the totals are expected to be closer to a quarter-inch at the most, Mehle said.

“We will see a lot of heavier rain the higher up you go, and some of the lower areas may struggle to get some,” he said.

The National Weather Service on Monday announced a winter storm warning for the Sierra Nevada from 10 a.m. today to 6 p.m. Wednesday. The heaviest snowfall of the season so far is expected, with chain controls and travel delays on mountain roads, white out conditions and 12 to 18 inches of snow above 6,500 feet and 2 to 3 feet at higher elevations. Up to a foot is expected in the Central Sierra, including Yosemite National Park.

The snow is arriving just in time for ski resorts, many of which traditionally open around Thanksgiving with a mix of natural and machine-made snow.

“That will end fire season in the Sierras for sure,” Clements said.

This year has been a fire season for the record books. Dry trees, brush and grasses due to a drier-than-normal winter last year — combined with freak lightning storms in August and millions of dead trees left over from the five-year drought that ended in 2017 — created the worst fire season in modern California history. More than 4.1 million acres have burned so far this year, an area more than 11 times larger than the city of Los Angeles.

The storm will mark the second time in a week that rain has come through the Bay Area. A system last week coated the area with barely measurable precipitation.

T hat system moved through the area quickly, and forecasters anticipate this one will do the same, Mehle said. The bulk of the rain for this system will fall Tuesday and into early Wednesday. Light rain is possible Thursday in the North Bay mountains, but Mehle said dry weather will replace it and remain until at least just before Thanksgiving.

“We’re keeping an eye on the next round possibly being then,” he said. “But we have to wait to see how it develops.”