ATLANTA: Southerners in large parts of Louisiana and Arkansas awoke to tornado watches two days before Christmas. Forecasters warn that powerful tornadoes, thunderstorms and flooding could soon spread across Mississippi, Alabama and parts of Georgia.

The national Storm Prediction Center in Norman, Oklahoma, projects that the highest threat for tornadoes Wednesday will be in a region of 3.7 million people in northern Mississippi, western Tennessee, and eastern Arkansas, as well as slivers of southeast Missouri, southern Illinois and western Kentucky.

Forecasters at the Storm Prediction Center say "multiple tornadic supercells" will be possible in that area from midday Wednesday through the afternoon.

In Alabama, heavy rains overnight left some downtown Mobile streets flooded during Wednesday morning rush hour. The city was under a tornado warning before the workday began. No touchdowns or damage were reported.