Harvey will still pack enough punch to continue flash flooding and trigger isolated tornadoes in parts of the central and southern United States through Friday night.
Motorists over the Ohio and Tennessee valleys, as well as the southern Appalachians, should be prepared for drenching rain and slow travel at the very least into Friday night.
However, motorists should use caution in downpours when venturing into low-lying urban areas, as well as rural locations along small streams. A sudden rise in water levels may occur.
The greatest risk of flash flooding will be centered on Kentucky and southern West Virginia during the day Friday.
During Friday night, the area at greatest risk will expand to much of West Virginia, portions of Ohio, Virginia and western Maryland. Portions of northern and eastern Kentucky will still be at risk as well.
Farther north, a swath of dry and chilly air will keep rain from reaching St. Louis, Chicago and Detroit.
Outside of the prime flash flood risk area, very isolated downpours and corresponding urban flooding can occur as far south as the Gulf coast and as far east as the Atlantic coast.
"In terms of severe thunderstorms, Harvey will still create favorable conditions for isolated tornadoes to end the week," according to AccuWeather Storm Warning Meteorologist Richard Schraeger.
This risk will extend from eastern Tennessee and central Kentucky to southwestern Virginia, western North Carolina, South Carolina and eastern and southern Georgia into Friday evening.
People are urged to take tornado warnings seriously since there may only be a few minutes to move to safety.
Dry air will sweep from west to east across the region early this weekend and end the risk of heavy rain and isolated tornadoes.