Dramatic Monsoon Storms, Flash Flooding Predicted For Palm Desert

PALM DESERT, CA — Scattered thunderstorms are expected to develop over parts of the Inland Empire Wednesday, signaling the first monsoonal activity of the summer season across the region, according to the National Weather Service. Those storms may lead to flash flooding in parts of Riverside County, they reported Wednesday morning.

The risk of flash flooding is low in Riverside County mountains and deserts, and rainfall amounts overnight and Wednesday morning are expected to be minimal.

Thunderstorms are expected throughout Wednesday and isolated flash flooding is possible in Idyllwild-Pine Cove, Indio, Palm Springs, Cathedral City, Palm Desert, La Quinta, Coachella, Borrego Springs and Banning.

Scattered showers will likely develop Wednesday evening with movement from south to north, according to reports from the NWS.

Meteorologists said humidity levels are climbing amid elevated temperatures, with a moisture stream pushing into Southern California from Mexico, generating conditions ripe for convective-driven instability, which will likely be most prevalent Wednesday in the deserts and around the mountains.

"By Wednesday afternoon, monsoonal moisture will be fully in place, with surface mass convergence," the NWS said in a statement. "This looks to provide the best opportunity of thunderstorms to develop. Most cells will produce .25 to .50 inches. There is a low risk of flash flooding over the mountains and deserts Wednesday afternoon, into the early evening."

Prognostication charts published by the NWS showed dueling high- and low-pressure systems over Southern California on Wednesday afternoon, with the possibility of scattered thunderstorms in most of Riverside and San Bernardino counties.

"There may be just enough moisture remaining Thursday to allow for isolated showers or thunderstorms to develop over the mountains ... before dry weather returns Friday and into the upcoming weekend," the agency stated.

No watches or warnings have been issued yet, but they could be posted anytime, depending on the intensity levels of the storms.

"The threat of dry lightning is low," the weather service said, indicating a low probability of wildfire outbreaks in connection with the unstable energy.

In the Riverside metropolitan area, the swelter will continue for the rest of the week, with highs generally in the mid- to upper 90s and lows in the mid- to upper 60s.

Triple-digit heat will remain the norm in the Coachella Valley, with the mercury topping out between 105 and 110 degrees going into the weekend, while overnight temps won't fall much below 80. In the Temecula Valley, peak temperatures are expected to hover in the upper 80s to low 90s, with lows falling to around 60 this week, according to the NWS.