band of extreme weather predicted to hit an area including chicago , detroit and st. louis , as well as memphis , tennessee , and little rock , arkansas on thursday .
storm prediction center estimates that 57 million people live in an area with an ` enhanced risk ' of hail , damaging winds and tornadoes .
severe thunderstorms packing 80mph winds and large hail already made their way across central missouri on wednesday .
areas that do n't see strong storms on thursday could see heavy rain instead .