Flash flooding threatened parts of the Southland today as a combination of high heat and subtropical moisture created atmospheric instability, raising a chance of showers and thunderstorms, forecasters said.
The National Weather Service issued a flash flood watch that will be in effect in the San Gabriel Mountains and the Antelope Valley from 10 a.m. through this evening.
“With a good moisture source in place, any thunderstorm that develops will likely produce heavy downpours,” according to an NWS statement, which noted that the absence of strong winds would keep a thunderstorm largely stationary and give it “the potential to produce flash flooding.”
The weather service urged campers and hikers to remain aware of conditions and keep an eye on weather forecasts.
In the event of a thunderstorm, “expect dangerous cloud-to-ground lightning, gusty erratic winds …, small hail and brief heavy downpours, which could cause flooding across low-lying areas well as washes and arroyos,” the NWS warned in a statement on its website. “If you approach moving water across the highway, turn around. Don’t drown.”
The weather service also warned of a long-period south-southwest swell that would produce high surf and strong rip currents at beaches in Orange and San Diego counties. A beach hazard statement will be in effect in Orange County through Thursday evening.
Although no excessive heat warning was in force today, as was the case earlier this week, temperatures will remain high.