Southern California is expected to see greater impacts, including flooding, associated with this storm than Northern California, said David Roth, a meteorologist with NOAA’s Weather Prediction Center.

“It’s really going to be the area in and around the greater Los Angeles area that will see the highest rainfall rates, the biggest flash flood impact,” Roth said. 

The low-pressure system was swirling off the coast of Northern California early Wednesday morning, sending heavy rain to the San Francisco Bay Area. By 11 a.m., the center of the storm was drifting southeast off the coast of Central California, said Roth. The system is expected to dump rain over Central and Southern California as it continues to push southward Wednesday and Thursday. By Saturday, the storm is forecast to be over northwestern Mexico, NOAA said.

“The low will stream moisture into California, creating rain and isolated highest-elevation snow over the Sierra Nevada Mountains,” the agency said in a forecast posted Wednesday morning. “The storm will produce heavy rain over much of coastal California and inland.”

On Wednesday morning, Northern California, including the Bay Area, recorded the heaviest rain it’s expected to see from the system. Scattered showers are in the forecast Wednesday afternoon, and a shot of heavy rain is possible Wednesday evening, but it’s likely to be quick. By the end of the day, low-lying areas of the Bay Area are expected to have recorded 0.5 to 1.5 inches of rain, according to the National Weather Service. Higher amounts are likely in the mountains. The rain is forecast to be over in Northern California on Thursday, with Friday expected to be dry. 

Southern California is expected to become the storm’s focus Wednesday night into Friday morning, and the Weather Prediction Center said the system will bring a moderate risk of excessive rainfall to the region. “The associated heavy rain will create numerous areas of flash flooding with narrow canyons/gullies and burn scars the most vulnerable. Furthermore, many streams may flood, potentially affecting larger rivers,” the agency said.

From Wednesday through Friday, the National Weather Service is predicting that the area stretching from San Luis Obispo County to Los Angeles County will generally pick up 2 to 4 inches of rain, with mountains and foothills recording up to 4 to 8 inches. 

Roth said Santa Barbara County may see some of the heaviest rainfall in the state associated with this system, especially between 4 and 10 p.m. Wednesday. “We have some two-day rainfall totals around 7 inches, mostly in the Santa Barbara area,” he said.