KHOU 11 Meteorologist Pat Cavlin says it's impossible to determine exactly where the heaviest of rain will fall, but everyone in risky areas should stay aware.

At 9:58 p.m. on Saturday, the National Weather Service released a flash flood warning in effect until Sunday at 1 a.m. for Jackson and Cass counties.

Scholars and designers of early warning systems say that there are still huge gaps in our ability to predict flash floods and warn those at risk.

The National Weather Service released a flash flood warning at 7:31 p.m. on Saturday in effect until 11:30 p.m. for Delaware County.

In the Midwest, quarter-sized hail and an isolated tornado cannot be ruled out, while in the South, flood alerts are in effect for areas that were devastated by flash floods last week.

The National Weather Service released a flash flood warning at 1:17 p.m. on Saturday in effect until 3:45 p.m. for Franklin and Hampshire counties.

On Saturday at 8:38 p.m. a flash flood warning was released by the National Weather Service in effect until 11:45 p.m. for Franklin County.

Straighter, smoother streams flow more violently than those that meander due to a reduction in friction. Areas with steeper terrain can see water accelerate downhill at a much faster rate causing a more destructive flash flood than flatter, open areas.