Showers and a few thunderstorms associated with a cold front will shift eastward across the Appalachians, reaching the Atlantic Seaboard later Tuesday and Tuesday night.  In the front’s wake, frost and freezes could threaten temperature-sensitive crops—including blooming fruits and emerged corn—as far south as the middle Mississippi Valley, the Ohio Valley, and the middle Atlantic States.  Meanwhile, a new storm system will cross the Northwest before reaching the nation’s mid-section late in the week.  That storm could result in additional heavy precipitation across the north-central U.S.

…