San Diego, CA – A Flood Watch will go into effect late tonight across much of Southern California as a strong Pacific storm brings periods of heavy rainfall and possible thunderstorms through Saturday evening, according to the National Weather Service San Diego.

According to the NWS, the Flood Watch covers a wide portion of the region, including San Diego County, Orange County, the Inland Empire, the Coachella Valley, the Apple and Lucerne Valleys, San Bernardino and Riverside County Mountains, and the Santa Ana Mountains and Foothills. The watch begins late Friday night and continues through Saturday evening.

Forecasters say excessive runoff may result in flooding of creeks, streams, low-lying roads, and flood-prone areas. Urban flooding is also possible, especially in spots with poor drainage. The NWS notes an elevated risk of debris flows near recent burn scars, where intense rainfall can trigger fast-moving runoff and mud.

A Pacific storm system will move in overnight, bringing areas of heavy rain along with a chance for thunderstorms. According to the NWS, rainfall rates may increase during the day Saturday, heightening the threat of flooding as additional rounds of showers move through the region.

Residents in flood-prone areas are urged to monitor forecasts, prepare for rapidly changing conditions, and remain alert for any Flood Warnings that may be issued.