Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

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.

The Flood Watch covers most of the state, barring some counties in northwestern and southeastern Oklahoma, through at least Sunday afternoon.

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.

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.

At 4:59 p.m. on Saturday, the National Weather Service issued an updated flash flood warning in effect until 8 p.m. for Lackawanna, Luzerne and Wayne counties.

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.

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.