Los Angeles — and burn areas throughout the region — brace for rainstorm beginning Monday

Southern California is bracing for the first major rainstorm to hit the region in nearly a year, beginning Monday and with forecasters warning that the heaviest rain is expected in some burn areas.

Almost 4 inches of rain is expected in Santa Barbara and Ventura counties from Monday evening through Tuesday morning. The nearly extinguished Thomas fire, which stretches across these two counties, has charred more than 281,000 acres since Dec. 4, making it the largest fire on record in California.

“Unfortunately it’s centered almost exactly where the Thomas fire was,” said Kathy Hoxsie, a meteorologist with the National Weather Service.

The best chance for thunderstorms throughout the region will fall on Tuesday.

“The problem with thunderstorms is that they can produce a lot of rain intensely in a small area,” Hoxsie said. “That would be another threat to these burn areas.”

People continue living under the Fourth Street bridge a day before rain is to begin falling in the the area.

(Robert Gauthier / Los Angeles Times )

When a fire sweeps through an area, it not only burns the vegetation but damages the soil itself, Hoxsie said. The intense heat makes the soil unable to absorb water the way it normally would.

“It doesn’t soak in the way it should; it runs off,” Hoxsie said. “With that kind of heavy rain, if we’re talking 4 inches in 12 hours, that will cause some problems anywhere.”

“We’ve really had no recovery time” from the fires, said Tom Stokesberry, a public information officer assigned to the Thomas fire. “We’re recommending that the public not visit the [Los Padres] National Forest for the next few days and let this storm pass and see what damage might come of it.”

Downtown L.A. is looking at about an inch of rain over a 12-hour period beginning at midnight Monday, when the storm front will pass through the county. The mountains above the San Gabriel Valley is “kind of a secondary hot spot,” where 2 ¼ to 3 inches of rain is expected, Hoxsie said.

There are 172 debris basins throughout the county’s flood control district, with the vast majority in the San Gabriel mountains, said Kerjon Lee, a spokesperson for the L.A. County Department of Public Works. The basins are strategically placed in the mouths of canyons to catch flowing mud and debris.

All but three of the debris basins have been almost completely cleared, Lee said. Workers began preparing the basins in October in anticipation of the storm season.

“We’re preparing the system for that 1% chance that you’re going to have a 100-year storm,” Lee said.

Officials are also alerting residents specifically within the Kagel, Lopez and La Tuna Canyon communities about the potential for evacuations because of mudslides.

“Anywhere that’s had a fire in the past five years...has the potential for mud and debris flow,” added Capt. Keith Mora, of the Los Angeles County Fire Department.

Throughout downtown, some of the homeless population said they were unaware of the impending storm.

“My God — I guess the only thing to do is load up my car. Or else we have to start sandbagging,” said Will Mendez, who lives in a homeless encampment under the Fourth Street bridge. “We have plenty of sand here. Maybe we make our own bags out of sheets.”

Diane Morachis, 34, was also caught unaware about the expected deluge.

“I haven’t watched the news in a year. I don’t know anything about any storm,” said Morachis, who lost her job last year at a payment processing company.

Mark Jefferson puts sand bags in front of his house in Kagel Canyon before a storm hits the the Creek fire burn area.

(Wally Skalij / Los Angeles Times )

“When you end up on the streets, you can’t get attached … to things,” she said. “Out here, we are degraded every day and our stuff is the least of our worry when it comes to rain.”

Before the ground gets thoroughly muddied, Morachis said she will have to resort to seeking favors from friends.

“There are still some people that I know in my regular life — and I say regular life because being homeless is not normal for me — and those people I’ll have to turn to to ask to stay the night,” she said. “Lucky for us, we’re young. It’s the older homeless people I worry about.”

Workers at the Midnight Mission on skid row plan to open up their dining room during the storm to house an additional 100 people, said Georgia Berkovich, the mission’s public affairs director. Individuals can also find shelter under awnings where heaters will be provided while staff distributes ponchos and donated clothing.

“Good weather or bad weather, the conditions on skid row are the worst they’ve ever been and we’re prepared to do what it takes to help,” Berkovich said. “We’re here 24/7 and as the homeless crisis intensifies, so do our services.”

Lingering showers are expected Wednesday, said Hoxsie, of the National Weather Service.

“Then we can hopefully breathe easier Wednesday afternoon,” Hoxsie said. “That’s if we don’t have hillsides continuing to slide or anything. But the weather itself should be over. The effects might not be over, but the weather should be.”

anh.do@latimes.com | Twitter: @newsterrier

brittny.mejia@latimes.com | Twitter: @brittny_mejia

UPDATES:

5:50 p.m.: This article was updated with new information from the National Weather Service.

4:35 p.m.: This article was updated with comments from the director of the Midnight Mission on skid row.

2:50 p.m.: This article was updated with comments from county officials and some homeless people living downtown.

2:10 p.m.: This article has been updated with comments from the county’s public works department.

12:35 p.m.: This article has been updated with comments from fire officials.

11:40 a.m.: This article was updated with details from a meteorologist with the National Weather Service.

This article was originally published at 8:55 a.m.