 The next day a dry line , which separates the drier air from the more moist and humid air , formed ahead of the cold front across the Texas and Oklahoma Panhandles and tracked eastward . The high humidity levels with dew points in the 70s ° F ( low 20s ° C ) , temperatures that in many areas were near 80 ° F ( 27 ° C ) , strong wind shear and the presence of the dry line helped develop the instability to produce severe thunderstorms across the Midwest and Southern Plains on October 17 . 
