A flash flood watch has been issued for Riverside and San Bernardino counties, effective Friday afternoon through Friday evening, the National Weather Service (NWS) reported Thursday night.
Afternoon heating and a deep moisture layer will bring the potential for large, slow-moving thunderstorms capable of producing heavy rainfall, prompting flas floods, the weather service reported.
The latest advisory includes the San Bernardino, San Diego and Riverside county moutains, the Apple and Lucerne valleys, the Coachella Valley and San Diego County deserts, according to NWS.
Particularly vulnerable to the expected rainfall are recently burned areas, officials said.
Officials are warning motorists not to drive into areas where water covers the roadway because the water's depth may be deceptive, and are urging residents to move to higher ground should the conditions in their area worsen.
Earlier in the afternoon, Riverside and San Bernardino counties were under flash-flood and severe-thunderstorm warnings. Doppler radar indicated flash flooding in the previously warned area, which included the cities of Riverside, Moreno Valley, San Bernardino and Rialto.
A thunderstorm capable of producing damaging winds in excess of 60 mph was spotted approaching the 215 and 10 Freeways near Loma Linda and Redlands at about 3 p.m. Thursday, officials said. That storm was traveling northwest at about 5 mph.
Heavy rain fell between Mountain Pass and Nipton Thursday afternoon. Officials estimate that as of 4 p.m. Thursday, about 2 inches of rain had fallen across basins which drain toward Nipton and Cima roads east of the 15 Freeway Nipton Road Junction.
The Inland Empire can expect more severe weather to start the weekend, according to NWS.
Yucca Valley, Banning, Beaumont and Desert Hot Springs were all dry as of 4 p.m., raising concerns of dry lightning, the chance of which is expected to increase Friday. That weather phenomena was identified as the cause of a nearly 3,000-acre wildfire in a rural area east of Temecula Wednesday.
Highs between 92 and 101 degrees are expected Friday in Riverside and San Bernardino counties. The chance of extreme weather will linger throughout the weekend.
After more than a week of triple-digit heat, some in the Inland Empire are welcoming the storms.
“It lessens the effect of the heat. Though the humidity is higher, it provides relief,” said Danyte Mockus, epidemiologist for Riverside County Department of Public Health.
Mockus recommends residents wear loose clothing, limit outdoor activity, and stay hydrated to combat the swelter.
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