A cold, “almost unprecedented” September storm is working its way toward the Southland, bringing the threat of showers, thunderstorms and snow at higher elevations from this afternoon until tomorrow. National Weather Service forecasters said the chance of measurable precipitation in the form of showers and thunderstorms in the Greater Los Angeles area stands at 30 percent today and 70 percent both tonight and tomorrow. In the Antelope Valley, it was set at 20 percent today and 60 percent tonight and tomorrow, while on Santa Catalina Island, it stands at 60 percent today, 70 percent tonight and 60 percent tomorrow. A Flash Flood Watch was to go into effect tonight in areas of Catalina recently denuded by a wildfire. Forecasters rainfall totals will be highly variable because of the showery nature of the expected precipitation. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set!