Heavy mountain snow with brief snow squalls across thenorthwestern U.S. through tonight into Tuesday.Moderate to heavy snow from North Dakota into northern Minnesota onTuesday.Severe thunderstorms possible Tuesday evening/night from the Midwest tothe Ohio Valley/Great Lakes.Record warmth engulfing much of the mid-section of the country will bedrastically colder by Wednesday with sub-zero will chills across thenorthern Plains and upper Midwest.The stage is set for a dome of arctic air that has...