Moderate to heavy rain fell in the Glendora and Azusa area, where the Colby Fire burned nearly 2,000 acres in 2014, leaving little vegetation to hold water back.
The flash-flood warning was set to expire in east central L.A. County at 3:45 p.m.
Meanwhile, firefighters rescued a man trapped by the fast-rising Los Angeles River as the system moved in and dumped up to .75 inches of rain by mid-morning. The man was uninjured after being pulled to safety along the riverbank area east of downtown known for homeless encampments.
A crash involving two trucks closed the southbound lanes of the 5 Freeway at Smokey Bear Road in Lebec near the Grapevine. There were no immediate reports of injuries.
Motorists were warned to use caution on mountain roads, where snowfall above 5,500 feet could create icy conditions and poor visibility.
Angeles Forest Highway was closed between Aliso Canyon Road and Angeles Crest Highway, as was Upper Big Tujunga Canyon Road between Angeles Forest and Angeles Crest highways.
Big Tujunga Road was also closed between Vogel Flats Road and Angeles Forest Highway. Lake Hughes Road is closed between Warm Springs to Newvale Drive in Lake Hughes.
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