A state of emergency has been dcelared for Butte County as California is bracing for the arrival of an atmospheric river that forecasters warn will bring heavy rain, strong winds, thunderstorms and the threat of flooding even as the state is still digging out from earlier storms. Gov. Gavin Newsom proclaimed a state of emergency this (Thursday) morning to support storm response in 21 additional counties including Butte, Plumas, Sacramento and Yuba. The flood threat (starting Thursday) will come from the combination of rain and melting of parts of the huge snowpack built in California's mountains by nine atmospheric rivers early in the winter and later storms fueled by a blast of arctic air. Storms are expected to last through mid-March.