The National Weather Service in Huntsville has issued a Flash Flood Watch for the Entire Tennessee Valley through 7PM Wednesday evening. Along with this watch flash flood warnings are being issued as they're needed. A flash flood warning is issued when flooding is imminent or already occurring. These warnings remain in effect for Southern Madison County and Marshall County in Alabama.
NOAA's Weather Prediction Center outlines a SLIGHT RISK of flash flooding Wednesday; some model guidance projects as much as 5 to 8 inches of rainfall through Thursday (most of it coming on Wednesday).
Be watchful for any flooded roadways as heavy rain is falling. This won't affect every single community. In fact, some may get very little rain while others get 2" to 5" in all. It will be very uneven, so the impact won't be felt equally from one county to the next.