(CNN)A slow-moving system will dump three to six inches of rain on the lower Missouri Valley over the next three to four days, creating a dangerous flooding threat.
Some rivers in the area are high or near flood stage, and the ground is already saturated in many places, making the situation especially concerning.
The system will move from Oklahoma through Arkansas, Missouri, Kentucky and Tennessee over the next several days, dumping torrential rains along the way. Urban flooding, stream flooding, and river flooding are expected.
Memphis and Nashville in Tennessee, Louisville, Kentucky, and Springfield, Missouri, will see localized downpours on top of an already saturated ground, causing much of it to run off. People living near small streams and rivers will be at greatest risk.
"It's going to rain for days," CNN Meteorologist Chad Myers said. "These storms are going to be popping up in the same spots that we had rain yesterday and the day before, and the day before, and that's the real threat. The ground is really saturated."
The National Weather Service has issued flash flood watches for parts of southern Illinois, southern Missouri, and western Kentucky as of Thursday. More are expected to be issued as the system moves east.
Tributaries near Memphis are already near flood stage, and localized heavy rain and low terrain will put the city and surrounding regions at a high risk for dangerous flooding. The Memphis area could see as much as 10 inches of localized rainfall, according to Myers. Evansville and Louisville, Kentucky, are also at a high risk due to nearby tributaries.
"There are many rivers that feed into the Ohio River and go right through these towns," Myers said. "And they could come up very rapidly."