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The first of two storm systems will make its way into Southern California Wednesday night but most of the rain won’t arrive until Thursday.

“The main brunt of the system that comes through tomorrow brings about an 8 to 10-hour window of rain, but there are a couple of hours in there where we get some really strong rain, which poses the threat of some runoff and some flood issues,” KTLA Meteorologist Henry DiCarlo said.

The system is expected to bring 1 to 2 inches of rain to the Los Angeles County coasts and valleys with 2 to 5 inches forecast for the mountain and foothill areas Wednesday through Thursday, according to the National Weather Service.

A forecast of the timing and intensity of this week’s rain is shown in a graphic produced by the National Weather Service.

“We’re tapping into that atmospheric river, so that’s going to help aid in a little bit more rainfall … and then a second storm system will move in behind it late Sunday into Monday,” Henry said.

A flood watch is in place for Riverside, San Bernardino and Orange counties from Thursday morning through Friday morning, according to the weather service.

“Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations,” the weather service stated.

The system could bring a significant amount of snow to our local mountains with 1 to 4 inches down to 5,000 feet, 6 to 12 inches between 6,000 and 7,000 feet, and 12 to 24 inches above 7,000 feet, according to the weather service.

This week's storm outlook provided by the National Weather Service.
This week’s storm outlook is provided by the National Weather Service. Jan. 31, 2024.

Winter storm warnings due to heavy accumulations of snow have been issued for the San Gabriel mountains, San Bernardino, Riverside and Ventura County mountains through late Thursday or early Friday.

Motorists are advised to avoid mountain travel as significant delays are expected. If you are going to the mountains, officials urged drivers to bring winter emergency supplies.

Dry skies with some sunshine should return Friday and Saturday before the second storm arrives late Sunday, Henry said.

This second system will bring a chance of rain through Tuesday and has the “potential to be more impactful,” bringing higher rain totals, lower snow levels and potential for flood impacts, the weather service stated.