Active weather will move into the eastern third of the nation Monday as an intense storm system over Minnesota lifts northeastward across Lake Superior into southern Ontario.
Showers, periods of heavy rain and thunderstorms will accompany this system, developing from parts of the Upper Mississippi Valley through the Great Lakes and parts of the Northeast. Showers in the Lower Great Lakes and Northeast will be enhanced by an associated warm front that will lift through the northern parts of the Ohio Valley and the Mid-Atlantic. Meanwhile, severe weather activity will be possible within the vicinity of an associated cold front that will extend southwestward from this system. Storms in areas from New York and Pennsylvania southwestward through the Tennessee Valley to Mississippi and Alabama may turn severe with large hail and damaging wind through the day.
Behind this system, strong winds and a much cooler airmass will settle over the Midwest. Thus, significantly cooler daytime highs are expected.
In the West, a cold front will produce rain and mountain snow as well as gusty winds along the coast from Washington to parts of northwestern California as it moves through the Pacific Northwest.
Temperatures in the Lower 48 states Sunday ranged from a morning low of 5 degrees at Monarch Pass, Colo., to a high of 97 degrees at Laredo, Texas.