LOS ANGELES (CNS) - Light rain fell across most of the Southland Wednesday, but it was only a precursor to what forecasters are calling a potentially dangerous storm expected to arrive by late Thursday, raising fears of flooding, mudslides and debris flows, particularly in the recent burn areas, where evacuations could be ordered.

Los Angeles County and city 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.

Sheriff Robert Luna said formal evacuation warnings will likely be issued sometime Wednesday morning, possibly followed by evacuation orders depending how the storm develops Thursday.

"Please, if evacuation orders are made, ... keep your safety in mind," 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.

A flash flood watch has been issued by the National Weather Service for the bulk of Los Angeles County, and much of Orange County, which will be in place from Thursday afternoon through Thursday night. Forecasters have said the strongest portion of the storm system is expected in the Los Angeles area beginning Thursday evening and continuing until early Friday morning.

The NWS has already 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 is expected to fall on Wednesday, but by the time the brunt of the storm moves through the area, 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.

Los Angeles County Supervisor Lindsey Horvath said she understands the PCH closure is difficult for resident in the Palisades and Malibu areas, but authorities will only reopen it "when it's safe."

"We know that this can also contribute to emergency fatigue," Horvath said. "Staying on high alert for this extended period of time is challenging. Stay with us. Stay informed. We're here to protect you and work with you to keep you, your family and your community safe."

Bill Handel