The storm system that delivered extreme weather across the nation’s mid-section over the last few days will weaken and drift across eastern Canada, although a trailing cold front will continue to spark showers and thunderstorms through Tuesday in parts of the southern and eastern U.S. In the storm’s wake, chilly conditions will linger across the Great Lakes and Northeastern States, with freezes possible in both regions. Toward week’s end, the focus for cool, stormy weather will return to the northern Plains, where yet another storm system will begin to intensify.