The south-central U.S. is facing a "heightened" risk of flash flooding into Thursday following days of deadly storms across a region that's spanned from Texas to the Northeast, the National Weather Service warns.

Severe storms are still underway on Tuesday morning in northern Texas and Oklahoma as golf ball-sized hail has already been reported early Tuesday in Oklahoma amid numerous severe thunderstorm warnings. Meanwhile, a severe thunderstorm watch has been issued for northern Oklahoma and southern Kansas until 10 a.m. CT.

Significant flooding was already underway early Wednesday in southern Oklahoma and adjacent north Texas.