The first of two storms expected to batter the Southland began bearing down on the region today, with significant rainfall hitting Thursday morning — ahead of more dramatic downpours anticipated early next week.

Long Beach got rain at a rate of more than half an inch per hour for a good portion of the morning, according to the National Weather Service, which issued a flash flood warning until 11:15 a.m.

In West Long Beach, four cars got stuck in deep water where Sepulveda Boulevard turns into Willow Street, according to the Long Beach Fire Department, which dispatched a rescue team to help get the people inside to safety.

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The water was so deep it pooled around drivers’ feet as they drove into it, LBFD Capt. Jack Crabtree said.

Vehicles in the Park Estates neighborhood were also seen partially submerged in water.

Roadway flooding was reported throughout the city, including on the 710 Freeway where all southbound lanes were closed for a time at Pacific Coast Highway, according to Caltrans.

Traffic backs up into one lane on Willow Street at Studebaker Road as crews pump out mass amounts of water from the intersection in Long Beach, Thursday, Feb. 1, 2024. Photo by Thomas R. Cordova.

Drivers were warned to avoid travel on local roads for the next two hours, the weather service said at 8:30 a.m.

“We are aware of flooding throughout the city,” the Long Beach Police Department tweeted just after 9 a.m. “Please plan your travel accordingly and drive safe.”

According to weather officials, the Southland will likely see the brunt of the rainfall just in time for the Thursday morning rush hour, with the strongest downpours expected to occur during a one- to three-hour period “when the primary frontal band moves through.”

Forecasters predicted rain rates of about a half-inch per hour, with some localized areas receiving 0.8 inches per hour.

Coastal and valley areas are expected to receive 1 to 2 inches of rain during the Thursday storm, with foothills and mountains potentially seeing 3 to 5 inches.

“While the rain will be quite heavy at times, due to the shorter duration of the event impacts are expected to be relatively minor with mainly typical roadway ponding of water and slick driving conditions and flood advisories should be sufficient to handle this event,” according to the NWS. “However, with a 10-20 percent chance of thunderstorms, rain rates in very localized areas could be high enough to require a flash flood warning.

Flooding has been reported in some areas already including the McClure Tunnel in Santa Monica and on parts of Pacific Coast Highway. Parts of Pacific Coast Highway in Huntington Beach between Seapoint Street and Warner Avenue are closed in both directions because of flooding. The westbound Balboa Boulevard on-ramp on the 118 Freeway was closed because of flooding. Rocks have been reported blocking parts of Malibu Canyon Road.

Slippery conditions are causing cars to spin out on freeways in Los Angeles and Orange County and resulting in road closures. California Highway Patrol is reporting at least 50 spinouts and crashes on freeways and roads in the central Los Angeles area.

A flood watch will be in effect for most of Orange County from Thursday morning through Friday morning. A high surf advisory will also be in effect for Los Angeles and Orange County beaches from 2 a.m. Thursday through 6 a.m. Saturday, with waves of up to 9 feet possible in the O.C., and potentially reaching up to 12 feet at west-facing shorelines in L.A.

After the main brunt of the storm passes through, the rain should largely taper off by Thursday afternoon, although scattered showers are likely to continue into Thursday evening or possibly Friday morning in northern areas of Los Angeles County.

Thursday’s downpour, however, will only be a preview of what’s to come beginning as early as Sunday, when the area will be hit by what forecasters are calling “the largest storm of the season.”

The storm is “forecast to spin down the coast and lift an atmospheric river into and across Southern California,” according to the NWS.

“While the exact timing, rates and amounts are still uncertain, it is very likely that this will be a serious two- to three-day storm system,” forecasters said.

City News Service contributed to this report.