Storms May Bring Flooding in a Flash to Los Angeles, Las Vegas and Phoenix Areas This Week

By Alex Sosnowski, AccuWeather.com Senior Meteorologist

July 30,2015; 11:48PM,EDT

 

 

The risk of drenching and locally gusty thunderstorms has expanded to parts of Southern California, Arizona and Nevada.
According to AccuWeather Senior Meteorologist Ken Clark, "While the storms will tend to be very spotty when compared to a couple of weeks ago, they have the potential to bring heavy rainfall."

Flash Flood Threat Across Southwest and Southern California

The storms during the middle of July produced general rainfall ranging from a few tenths of an inch to just over an inch in Southern California. The rare mid-July rain was associated with moisture from both the Southwest monsoon and Dolores.
The spotty storms for the second half of this week will rattle the mountains and valleys surrounding Los Angeles and San Diego, as well as Las Vegas, Nevada, and Phoenix and Flagstaff, Arizona. The thunderstorms will also spread north to the Sierra Nevada.

It is not out of the question for a stray shower or thunderstorm to drift to the coast of Southern California into Thursday night, but many places will stay dry.
On Friday, Clark expects that the thunderstorm activity in the mountains and deserts of Southern California will not be as widespread "but could still be locally heavy."
The bulk of the storms will occur during the late afternoon and evening hours, but there will be some exceptions.
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The storms will tend to be rather slow-moving and can put down a great deal of rain in a short period of time.
The storms have the potential to bring 0.25 of 0.50 of an inch of rain in about an hour, which is enough to cause flash and urban flooding. A small number of the storms can last longer and be more potent.
Tucson, Arizona, was smacked with 1.36 inches of rain in two hours during Tuesday evening. The storm produced wind gusts to 64 mph. A successful swift water rescue of two adults took place in the Rodeo Wash area in Tucson.

Arizona Monsoon Downpour Stirs Up Neighborhood Floods

Motorists should use caution when traveling through or along normally dry stream beds. In addition to rapidly rising water, quick runoff can push debris onto some roadways.
Lightning strikes are also a concern. People outdoors should seek shelter indoors as soon as the first clap of thunder is heard.
Many of the storms will produce little or no rainfall, so lightning could ignite new wildfires.