Tropical system brewing in Pacific expected to bring cooling, lightning, storms to SoCal

A tropical storm brewing in the Pacific is expected to move north over the next few days, bringing to Southern California increased humidity, cooler temperatures and a chance for significant showers and thunderstorms this weekend.

The moisture-laden system, which officials upgraded early Wednesday to tropical storm Hilary, is still strengthening off Mexico’s southerly coast but will likely dissipate by the time it moves into Southern California. Remnants from the system could bring some notable precipitation to the region as early as Saturday.

Effects from the storm, however, could be felt as early as Thursday, when temperatures should begin to slightly dip as humidity increases, said David Sweet, a meteorologist with the National Weather Service in Oxnard.

“We’re expecting a cooling trend into the weekend,” Sweet said.

The cooling trend is expected to bring some relief to Southern California’s warmest inland valleys — including the western San Fernando Valley and the Antelope Valley — where highs were expected to peak at about 105 or 106 Wednesday.

“We’re seeing temperatures that are about 5 to 10 degrees above normal,” Sweet said Wednesday. “Even though we don’t have a heat advisory out in those warmest locations, people should keep in mind it’s going to be pretty darn toasty.”

A heat advisory is in place for the Inland Empire, the Coachella Valley and the Riverside and San Diego county mountains through Thursday, with temperatures in some areas as high as to 115 degrees.

By the weekend, temperatures should drop into the mid-80s and 90s for inland areas, while the coasts will see highs in the 70s or 80s — though increased humidity will make those temperatures feel slightly warmer, Sweet said.

A chance of afternoon storms remains Wednesday for the Los Angeles, Riverside and San Bernardino County mountains and deserts, forecasts show. There is a potential for lightning strikes through the evening, as well as isolated flash flooding.

Even stronger storms are possible this weekend, with a chance for showers and thunderstorms beginning Saturday through Tuesday, as tropical storm Hilary‘s leftovers blow through the region.

Sweet said the exact track of the storm is still forming, but the greatest chance for storms and widespread showers is expected Monday.

“There’s going to be a lot of humidity and a lot of moisture with this,” Sweet said. “Some of [the precipitation] could possibly be heavy.”

Tropical storm Hilary is still several hundred miles off Mexico’s southwestern coast but becoming more organized as it moves northwest, according to the National Hurricane Center.

The system is expected to most strongly affect the Baja California Peninsula, as well as portions of southwestern United States, with rains, winds and some strong surf forecast for this weekend. Forecasts are showing increasing chances for heavy rain, with excessive rainfall and flash flooding possible, beginning Saturday through Monday for Southern California, much of Arizona and Nevada, and even states further north, such as Utah, Idaho and Oregon.