A threat of monsoonal thunderstorms across southwest California has been reported by the National Weather Service through Monday, and flash flood warning has been issued for coastal and other areas, including Malibu, through Saturday evening, 7:30 p.m.
A high pressure system centered over the front range of the Rocky Mountains will continue to provide a moist southeast flow aloft. The flow pattern will continue to steer monsoonal moisture and instability into Southern California through Monday, the NWS said. The leading edge of this moisture will bring a chance of thunderstorms to the mountains of Los Angeles and Ventura counties as well as the Antelope valley through the weekend.
In addition, there is a slight chance of thunderstorms to coastal and valley areas south of Point Conception through tonight. By Monday, an upper level low pressure system off the coast will begin to bring drier southwest flow into much of the forecast area, but a slight chance of thunderstorms will continue for the Los Angeles and Ventura county mountains as well as the Antelope Valley.
The weather pattern has the potential to bring significant monsoonal moisture into southwest California. As a result, any thunderstorms that develop could bring heavy rainfall, especially in the mountains and antelope valley. Since the upper level winds will be relatively weak through the weekend, storms will likely be slow Moving, increasing the threat for flash flooding.
A flash flood Watch is in effect through Sunday evening for the mountains of Los Angeles and Ventura counties, as well as the antelope valley. The flash flood watch may need to be expanded into the Santa Barbara County Mountains on Sunday. Some thunderstorms could produce gusty Winds, hail, and dangerous cloud to ground lightning. People planning outdoor activities in the mountains and deserts this weekend should closely monitor the latest National Weather Service statements, and be ready to take action if dangerous weather conditions develop.