A day after heavy rain, flooding and even a mud slide hit areas of the Inland Empire, a flash-flood watch was in effect Saturday for Riverside County and mountains and deserts of Southern California.
The National Weather Service had reported the flash-flood watch would be in effect until 8 p.m. for the Coachella, Apple and Lucerne valleys and the mountains and deserts of Riverside, San Bernardino and San Diego counties.
At about 2:15 p.m., radar showed thunderstorms weakening over the region, but a flood advisory remained in effect for urban and small streams for the afternoon.
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Areas that have recently burned in wildfires will be particularly susceptible to flooding and debris flows, the service said.
The weather service described flash floods as "very dangerous" and it warned drivers to avoid flooded roads. Most flood deaths occur in automobiles, the service said.
"Just 1 foot of flowing water is powerful enought to sweep vehicles off the road," the federal weather service said.
The warning came a day after hikers were stranded by mud and debris flow in Forest Falls, among other weather-caused incidents Friday.
"There's a chance of strong thunderstorms today in both counties, mostly in the mountains and deserts with possible localized flooding in and near thunderstorms,'' weather forecaster Mike Webster said.
Monsoonal moisture coming from Mexico's Sea of Cortez was creating extremely humid conditions north in Southern California. Slow-moving thunderstorms could cause very heavy rain and floods, Webster said.
The humid conditions will continue, Webster said, because strong winds haven't arisen to push the moisture out of the region.
''The humidity is going to remain on and off throughout the next couple weeks with a chance of thunderstorm formation over the mountains and deserts of San Diego and Riverside counties," Webster said.