26 million Americans under severe weather threat Saturday

More than 26 million Americans from the Heartland into the South are under a severe weather threat Saturday.

Severe thunderstorms are possible from Illinois to Texas through the evening, affecting cities including Houston, New Orleans, St. Louis and Little Rock, Arkansas. Numerous severe thunderstorms are possible in a region along the Missouri and Arkansas border.

The primary hazards will be strong, potentially damaging wind gusts and large hail -- though brief, isolated tornadoes cannot be ruled out. Frequent lightning is another concern.

The severe weather threat is expected to last from 4 to 10 p.m. ET, as a line of storms develops and moves through the threat area.

Areas of heavy rain and strong thunderstorms have started to sweep through parts of the northern Gulf Coast Saturday. A flood watch is in effect for cities including New Orleans and Biloxi, Mississippi. A severe thunderstorm watch is also in effect from New Orleans to Mobile, Alabama.

This storm system is forecast to continue to move up across the Great Lakes on Sunday, strengthening as it does so. A few scattered, strong thunderstorms could sweep through the central Appalachians into parts of the Southeast -- all associated with the trailing cold front. Snow, strong winds and plummeting temperatures are also expected to target parts of the Upper Midwest.

A winter storm watch has been issued for much of Wisconsin and extending into extreme southeastern Minnesota and portions of the Upper Peninsula of Michigan.

As much as 4 to 6 inches of snow is possible in parts of Wisconsin by Sunday night into Monday morning, while a light snow accumulation of 1 to 4 inches is possible across parts of Minnesota, Iowa, Wisconsin and the Upper Peninsula of Michigan.

Blowing snow will likely lower visibility in areas and could lead to travel impacts in the region.