Thunderstorm triggers a flash-flood warning in the Antelope Valley

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Brady Webush, left, and Johnny Byrne, both from Manhattan Beach, end their day in the El Porto area of Manhattan Beach. Weather in Los Angeles brought morning showers to the beaches and thunderstorms to other parts of L.A. County.

(Jay L. Clendenin / Los Angeles Times)

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A rainbow over Thousand Oaks after a day of thunderstorms and high humidity hit the Southland.

(Al Seib / Los Angeles TImes)

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People evacuate the beach, water and pier, including the U.S. Open of Surfing contest, as a thunderstorm with potential lighting approaches the area.

(Allen J. Schaben / Los Angeles Times)

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Huntington Beach police evacuate the beach as well as the water and pier, including the U.S. Open of Surfing contest, as a thunderstorm with potential lighting approaches.

(Allen J. Schaben / Los Angeles Times)

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A rainshower drenches a vehicle near the Rose fire outside Lake Elsinore.

(Glenn Koenig / Los Angeles Times)

By Alene TchekmedyianStaff Writer

Aug. 1, 2017 9:20 PM PT

A strong thunderstorm brought heavy rainfall to parts of Southern California on Tuesday afternoon, prompting weather officials to issue a flash-flood warning in the Antelope Valley in Los Angeles County.

Flooded roadways were expected until late evening in Lancaster and Palmdale, as well as on the 14 and 138 freeways, according to the National Weather Service.

Those areas were expected to receive 1 to 2 inches of rainfall an hour, which has the potential of causing dangerous flash flooding along roadways and normally dry washes, weather officials said. Dime-sized hail, gusty winds and frequent lightning were also reported.

Powerful winds caused downed power lines in Azusa, while a tree caught fire elsewhere in the region after getting struck by lightning, said Robbie Munroe of the National Weather Service.

In Huntington Beach, officials evacuated the city beach during the U.S. Open of Surfing after lightning strikes were reported in the area, police said. The beach has since reopened.

Areas burned by recent wildfires face a higher risk for debris flows and flooding, authorities said.

The rain “is associated with monsoonal moisture,” Munroe said. “We expect this moist energetic flow to continue at least through Wednesday night.”

In Temecula, a four-vehicle crash that involved an overturned big rig temporarily shut down the northbound 15 Freeway at Rancho California Road, snarling traffic for miles during rush hour, according to the California Highway Patrol. A tree fell onto the freeway in about the same area, also causing traffic delays.

A SigAlert was issued shortly after 4 p.m. and was lifted about an hour and a half later.

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Twitter: @AleneTchek