First of two storms arrive in Southern California, causing flooding

The first of two storms arrive in Southern California, bringing heavy rain and snow to the area on Thursday.

The most significant rainfall fell early Thursday morning during rush hour. The heaviest rain came down from 6 a.m. until 12 p.m. in Los Angeles County and from 9 a.m. until 12 p.m. in Orange County and Inland Empire. The heaviest snow will continue to fall in the San Bernardino and Riverside mountains until 3 p.m.

As of 10 a.m. Thursday, 2.3 inches of rain had fallen overnight at Long Beach Airport, while 2.4 inches fell at Los Angeles International Airport. Redondo Beach got 2.4 inches, while 2.16 inches were reported at UCLA. Downtown Los Angeles recorded 1.5 inches. Most valley areas reported around an inch of rain.

Flooding has been reported at the McClure Tunnel in Santa Monica and on parts of Pacific Coast Highway. Slippery conditions are causing cars to spin out on freeways in Los Angeles and Orange County and resulting in road closures.

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.

A winter storm warning will be in effect from 5 a.m. to 10 p.m. Thursday in the eastern San Gabriel Mountains, including Mount Wilson, Mount Baldy, Wrightwood and the Angeles Crest Highway. As much as 18 inches of snow could fall above 7,000 feet in the area, with 6 inches possible at 6,000 feet and 3 inches at elevations as low as 4,500 feet. The snow will be accompanied by winds gusting at up to 55 mph.

A previously issued winter storm warning was downgraded to a storm advisory in the western San Gabriel Mountains and the Golden State (5) and Antelope Valley (14) freeway corridors. In those areas, forecaster said light to moderate snow is anticipated above 6,000 feet, with a "dusting" of up to 2 inches at elevations as low as 4,500 feet. Winds in those areas will also gust up to 55 mph.

Traffic Alerts

• Westbound Balboa Boulevard on-ramp on the Ronald Reagan (118) Freeway closed due to flooding
• Rocks reported blocking parts of Malibu Canyon Road in Malibu
  
• Flooding reported at the McClure Tunnel in Santa Monica and on parts of Pacific Coast Highway
  
• Both sides of PCH closed between Seapoint Street and Warner Avenue in Huntington Beach due to flooding

For the latest traffic conditions, check KCAL's Next Traffic here.