An Atmospheric River is set to bring heavy rain to the coast and mountain snow to the Pacific Northwest and Northern California on Wednesday. Meanwhile, showers and thunderstorms will roll through the Lower Ohio, Tennessee, and Mississippi Valleys, bringing some heavy rain. There’s a chance of scattered flash flooding, especially in Louisiana and Mississippi. Across the central U.S. and Gulf Coast, temperatures will stay above average, while the Northeast and the West will see cooler air moving in.