Storm update: Lower rainfall amounts but higher risk of thunderstorms in Southern California

A cutoff low-pressure system that was about 800 miles southwest of LAX on Monday afternoon is expected to bring widespread showers and a chance of thunderstorms to Southern California Tuesday through Tuesday evening, the National Weather Service said.

A previously forecast atmospheric river component of the system carrying subtropical moisture is now expected to remain to the south, and rainfall will be associated with the cutoff low-pressure system, resulting in lower overall rainfall amounts, but a higher risk of thunderstorms.

A cutoff low will bring rain and a chance of thunderstorms Tuesday through Tuesday evening, as it moves toward Baja California by Friday.

(Paul Duginski / Los Angeles Times)

Brief heavy downpours, probably with thunderstorms, could still cause urban flooding or minor debris flows in recent burn scars. Small hail and waterspouts over coastal waters are also a possibility with the system, although gale-force winds are no longer predicted. There’s also a risk of lightning at the beaches.

Because it is a warm storm, snow levels will be well above the 7,000-foot elevation in the local mountains.

Rain totals are expected to be about an inch to 1.5 inches for the coast and valleys of L.A. County, with anywhere from 1.5 inches to 3 inches in the foothills and mountains. Rates of up to 1 inch per hour are possible in fast-moving thunderstorm cells. Rain will taper off to scattered showers on Wednesday.

Another colder storm is on tap for next Sunday and Monday. Rainfall is likely to be about a quarter-inch to an inch, but with a better chance of snow for the mountains.