The risk of drenching and locally gusty thunderstorms will expand northwestward over the balance of the week, reaching 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.”
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 during the balance of this week could reach as far west as Los Angeles and San Diego and as far north as Las Vegas, Nevada, and Phoenix and Flagstaff, Arizona.
The greatest chance of a thunderstorm in Los Angeles and San Diego counties is on Thursday.
The bulk of the storms will occur during the late afternoon and evening hours, but there will be some exceptions.
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.
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.