Southerners in large parts of Louisiana and Arkansas awoke to tornado watches on Wednesday, two days before Christmas. Forecasters warned that the pain could soon spread, with powerful tornadoes, thunderstorms and flooding possible across Mississippi, Alabama, Tennessee and parts of Georgia. The biggest 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, according to the national Storm Prediction Center in Oklahoma.