See When Rain From Tropical Storm Mario Could Bring Flooding, Lightning To SoCal

LOS ANGELES, CA — It's warm and muggy for swaths of Southern California as the remnants of tropical storm Mario move into the area, bringing the threat of flooding, lightning and thunder Wednesday night through Friday. Forecasters expect the impacts to vary greatly — with some areas likely to remain bone dry and others experiencing significant flooding.

"We've got this big wave of precipitation — it's just about hitting the southern border of our state currently," National Weather Service meteorologist Chandler Price told Patch just before 3 p.m. Ahead of that, the leading edge of the moisture already arrived earlier Wednesday, bringing isolated showers and thunderstorms as far north as the Central Coast.

The weather is a bit "complicated," Price said. The pattern is different from storms common in the winter, or even typical summer afternoon convention.

Already Wednesday afternoon, the National Weather Service recorded scattered showers moving into San Diego County.

"Storms are moving over southwest San Diego Co as well as the north-central mountains near Palomar," the Noational Weather Service posted on X. "Rain showers and thunderstorms will continue to move north and west tonight into Thu morning, then storms will gradually move eastwards Thu afternoon (most likely mtns and deserts)."

Residents in flood-prone or burn scar areas should be on alert, meteorologists warned.

"While most areas will get at least some rain, some areas may get little to none, while others just a short distance away could have flooding," the NWS office for Los Angeles County said.

Compared to more southern areas, Los Angeles County is expected to see a greater impact.

Chance of thunderstorms across Los Angeles County will hold steady at 10 to 20 percent until midnight and increase to 60 to 70% by 6 a.m. Thursday. That percentage chance will hold steady through midnight on Friday morning and taper off for the rest of the day, according to a timing forecast released Tuesday.

Residents should expect peak rain rates of a quarter inch per hour, but there may be localized spots of as much as an inch per hour.

Totals for the week are expected to be as high as 1 inch in some areas, though 0.1 to 0.5 inches will be much more widespread, according to the weather service.

"The big forecast question is how much is that going to weaken — because it is weakening currently," Price said.

In the San Bernardino Mountains and parts of the Inland Empire, Price expects "quite light" precipitation Wednesday evening after 6 p.m.

"Following that, we've basically got 24 hours of possible thunderstorms and rainstorms and those are going to be quite hit and miss," he said. The on-and-off thunderstorms are expected to continue through Thursday evening.

A flood watch is in effect for a range of areas across Southern California from late Wednesday into late Thursday, including in Malibu, the San Gabriel Valley, Antelope Valley, San Bernardino and Riverside county mountains, Coachella Valley and the San Diego County desert and mountains.

"Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations, including burn scar areas. Low-water crossings in the deserts may become flooded," the NWS warned.

Flood advisories were also in place earlier Wednesday in Ventura and San Diego counties.