LOS ANGELES (CNS) - The front end of a major storm system soaked the Southland overnight, but the brunt of the storm was expected to arrive later in the day, prompting a mix of evacuation warnings and orders due to the threat of flooding, mudslides and debris flows.

The storm system began with generally light rain Wednesday, with additional precipitation falling overnight and into the morning across a widespread area. According to the National Weather Service, the rain will intensify as the day wears on, with the brunt of the storm anticipated in Los Angeles County between 3 and 10 p.m.

"During those peak periods rain rates between a half and one inch per hour are possible with localized rates up to 1.2 inches per hour," according to the National Weather Service. "Those higher amounts are most likely to occur in the foothills and mountains, but can't rule out very heavy rain across the coastal plain either."

NWS Meteorologist Ariel Cohen said at a Thursday morning news conference that 4 to 9 p.m. will be the most critical period of the storm.

"That the time period when we're expecting the most intense rains coming through," Cohen said, saying the elevated rainfall rates can lead to significant flooding and burn scar debris flows.

A flash flood watch was issued by the National Weather Service for the bulk of Los Angeles County for Thursday morning through Thursday evening, with forecasters saying flooding and debris flows are possible, with the greatest risk in or near the Eaton, Palisades/Franklin and Bridge fire burn scars.

A flood watch will also be in effect from Thursday morning through Thursday night for most of Orange County.

Evacuation warnings went into effect at 7 a.m. Thursday for recent burn areas within the city of Los Angeles. Those orders affected:

-- Palisades Fire area: Getty Villa area, Highlands near the burned areas, Bienveneda area near Temescal Canyon Park, Reseda Blvd area/Marinette Road near Will Rogers State Park, Mandeville Canyon above Tanners Road.

Sunset Fire area: East and South of Runyon Canyon.

Hurst Fire area: Olive Lane in the Oakridge Mobile Home Park.

Some individual property owners in those areas whose homes were considered to be at heightened risk were given mandatory evacuation orders. As of 8:30 a.m. Thursday, those orders affected 106 homes in the Palisades Fire area, nine in the Sunset Fire area and four in the Hurst Fire area, according to Los Angeles Police Department Chief Jim McDonnell.

LAPD officers went to each of those affected homes to notify them of the order. Those homeowners also received electronic notifications, and door- hangers were left at their homes if police were unable to contact them. McDonnell also said no private contractors were being permitted in the Palisades burn area Thursday due to the evacuation warnings and orders.

The evacuation orders and warnings were expected to be in effect until at least 2 p.m. Friday, depending on the storm.

Evacuation warnings also stretched into the Malibu area. All Malibu campuses in the Santa Monica-Malibu Unified School District will be closed Thursday "due to road closures and weather concerns." District officials said the closure may extend into Friday depending on weather conditions.

Additional evacuation warnings were issued in the San Gabriel foothills near the Eaton Fire burn area, affecting thousands of residents. The city of Sierra Madre issued mandatory evacuation orders Thursday morning impacting nearly 1,000 residences.

Los Angeles County Sheriff Robert Luna said individual homes in areas patrolled by his agency were also given mandatory evacuation orders if their properties were considered at risk. Speaking to KNX News Thursday morning, Luna said authorities were taking a "surgical" approach to the mandatory evacuations to specifically target hopes considered at heightened danger.

He said mandatory evacuations as of Thursday morning were issued for nine homes in Altadena, 49 in Malibu, five in San Dimas and 35 in Palmdale.

In Orange County, evacuation warnings took effect in multiple areas at 8 a.m. Thursday for areas near the Airport Fire burn scar. The voluntary evacuation warnings will be in effect for Trabuco Canyon, Hot Springs Canyon, Bell Canyon, Long Canyon and Modjeska Canyon. Residents in those areas were "strongly encouraged" to evacuate by 8 a.m. Thursday. O'Neill Regional Park will also be closed Thursday, including the campgrounds.

A dormitory-style shelter was set up at the Foothill Ranch Library Program Annex at 27002 Cabriole Way, for Orange County residents leaving the area during the storm.

L.A. County public works crews have been working for days to prepare for the storm -- emptying debris basins, clearing storm drains and distributing sandbags to residents. In the Eaton Fire burn zone, the county Department of Public Works and the sheriff's department have also been warning residents living in homes that may be at high risk of damage from mudslides or flooding, and advising them to prepare to evacuate.

"Please, if evacuation orders are made, ... keep your safety in mind," Sheriff Robert Luna said. "They help to protect you and your loved ones from potential danger. Storms can bring sudden and severe conditions that make staying back home extremely risky. ... Please take necessary steps now to prepare. Pack an emergency kit, secure important documents and ensure that you have a plan in place for your pets and family members.

"And remember, if you're ordered to leave, you may be gone for several days. I cannot stand up here and tell you will be gone for 12 hours, 24 hours. We don't know. It depends on the weather and the post-weather events that will impact your specific neighborhood."

Luna said deputies have also been canvassing flood-prone areas such as the Los Angeles River to warn homeless people who may be camped there to relocate.

"Unfortunately, we witnessed numerous, numerous instances in the past of swift-water rescues where people were caught in dangerous, fast moving water, and obviously, we want to prevent that," he said.

The NWS has described the multi-day storm system as likely to be "the biggest precipitation producer so far this season."

Only about a quarter-inch of rain was expected to fall on Wednesday, but by the time the brunt of the storm exits the area on Friday, roughly 1 to 3 inches of rain are expected in most coastal and valley areas, with 3 to 6 inches anticipated in the foothills and mountains.

"The cold front will be capable of producing rainfall rates (that) meet or exceed the thresholds for debris flow in the burn scars ... and flood watches have already been posted for those areas," according to the National Weather Service. "However, minor flooding of roads is likely just about anywhere."

Los Angeles County Public Works Director Mark Pestrella said rainfall rates that exceed a half-inch per hour can lead to mud and debris flows, although factors such as topography, the soil system, geology and the status of the flood control system all contribute to the potential for such occurrences. He insisted, however, that crews have been working around the clock to ensure the county's 154 debris are clear and have the capacity to capture mud and debris that could descend mountain slopes.

"We are in a state of readiness with those facilities," Pestrella said. "We have the capacity for the size of storm that we expect to come with this storm."

He noted that the county has been working with federal agencies to develop a system for containing debris that may start flowing from within the Palisades and Eaton fire burn zones, hoping to contain any such flows on streets in those areas.

"This is unusual," he said. "We don't typically want any debris to end up in the streets."

But he said using a vast system that includes thousands of miles of K- rail and hundreds of thousands of sandbags, crews are hoping to capture debris before it reaches streets, but if it does, the flows will be diverted and contained on streets to prevent it from reaching waterways, which would lead to the ocean in the Palisades area.

Pestrella said that while the county has been working to notify residents in the fire zones whose homes may be at increased danger of experiencing mudslides, he urged residents who think they may be at risk to contact the county at 800-675-4357 to have their property evaluated. The service is available at any county location, not just the recent fire areas.

"This service is going to be provided right up to and to the point that we can no longer get to your properties," he said.

The Los Angeles County Department of Public Works was distributing free sandbags at the La Costa Post Office, 21229 Pacific Coast Highway in Malibu, for people in the Palisades Fire area. For those in the Eaton Fire area, the county was offering sandbags at Robinson Park, 1081 N. Fair Oaks Ave., and Victory Park, 2575 Paloma St., both in Pasadena.

A full list of locations where sandbags are available is at lacounty.pw/sandbags.

Los Angeles Mayor Karen Bass on Tuesday urged residents to be prepared to evacuate if necessary. Bass urged people to sign up for emergency alerts though notifyla.gov. And while the primary concern locally is in the recent burn areas, Bass stressed that the warning "is for all of Los Angeles," so residents across the city and region should be prepared.

The mayor said city crews -- much like county crews -- have been scrambling to prepare for the rain by clearing out catch basins, removing debris from storm drains and installing measures such as concrete barriers and thousands of sandbags, particularly in the Palisades Fire burn area.

Pacific Coast Highway remains closed to the public between Chautauqua Boulevard in Pacific Palisades and Carbon Beach Terrace in Malibu due to concerns about possible mud slides or debris flows. Topanga Canyon Boulevard was closed between PCH and Grand View Drive.

A series of road closures were also in effect in Malibu, including Malibu Canyon Road between Piuma Road and Adamson Flats. Residents only were being given access to Las Flores Canyon Road between Rambla Pacifico and PCH; Piuma Road between Cold Canyon and Rambla Pacifico roads; Rambla Pacifico between Piuma and Las Flores Canyon roads; Saddle Peak Road between Stunt and Tuna Canyon roads; Schueren Road between Saddle Peak and Piuma roads; and Tuna Canyon between Saddle Peak and PCH.

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