The first wave of winter has pushed into the lower 48 as a pro-nounced dip in the jet stream has developed over the western States. Curving from the Pacific Northwest to the Four-Corners region and then northeastward across the Rockies, this steering current has brought cold, Canadian air to the Intermountain West. Snow is falling in the mountains and many of the Great Basin cities have experienced their first hard freeze of the season.
Meanwhile, ahead of the trough, summer has returned to the High Plains and Midwest, with afternoon highs in the mid to upper 80s. As it moves eastward, the trough is forecast to "flatten out," keeping the cold air along the northern tier of States. Here in Missouri, southerly winds will bring a warm, humid flow from the Gulf of Mexico, producing conditions more typical of June than October. Should the cold air get close enough, atmospheric instablity and afternoon thunderstorms will develop, enhancing the illusion of summer. The battle of the seasons has begun; I'm betting on winter!
