 A cold front moved eastward across the middle and lower Mississippi River Valley before heading into the Ohio River Valley and stretched into the Mid-South portion of the United States.In front of the cold front, a warm, moist and unstable air mass spread northward from the lower Mississippi River Valley and northern Gulf Coast States into the middle Mississippi and Ohio River Valleys.There were already thunderstorms that had formed during the morning hours and the conditions would only become more numerous throughout the day.