Floodwaters threatened earthen levees protecting thousands of homes in the nation's midsection Tuesday, rising so fast in some places that panicked residents didn't have time to pile up sandbags.
Storms have unleashed more than a foot of rain across the region, and the forecast offered little hope for relief. Another, larger system was brewing along the same path, bringing several more days of rain and possible tornadoes.
The storm system dumped heavy rain on seven states and spawned at least one tornado Monday in Arkansas. The twister killed four people and blasted a path of destruction through the town of Vilonia, 25 miles north of Little Rock. Four others died in floods.
Thunderstorms, wind and low clouds tied up air traffic at seven airports in the Northeast and Midwest, and sent a Southwest Airlines plane sliding off a runway in Chicago.
No one was injured when Flight 1919, a Boeing Co. 737-700, ran off the tarmac in heavy rain at Midway Airport at about 1:30 p.m. local time, Whitney Eichinger, a Southwest spokeswoman, said in an e-mail.
The greatest flooding threat was in the southeastern Missouri community of Poplar Bluff, a town of 17,000 residents about 130 miles south of St. Louis. Six inches of rain fell there Monday, bringing the four-day total to 15 inches.
By midday, the deluge had caused the Black River to pour over a levee in 30 places. The flood wall extending from Poplar Bluff to the town of Qulin downstream was also breached in at least one place, where water gushed through a hole.
"Each heavy downpour, each hour that passes by with the water pushing on that levee, the likelihood of a failure is that much more possible," said Deputy Police Chief Jeff Rolland, calling it a "miracle" that the first hole did not develop until late morning.
In another area near the confluence of the swollen Mississippi and Ohio rivers, authorities debated a desperate plan to use explosives to blow a 2-mile-wide hole through a levee to ease the pressure on others.
Butler County Sheriff Mark Dodd said the water pouring through the levee was unlikely to make it far enough upstream to add to the threat facing Poplar Bluff, where about 1,000 homes had already been evacuated. But authorities planned to evacuate more homes closer to the breach, which was in a sparsely populated area.
Despite the punishment the region has already endured, the weather was expected to get worse -- and soon. Another line of storms moving through Oklahoma and Texas carried the same threat of tornadoes and flooding but over a broader area that stretched from Dallas to Louisiana and up to Memphis.
Greg Carbin, the warning coordination meteorologist for the National Weather Service's Storm Prediction Center in Norman, Okla., said having two systems develop back-to-back is unusual.
"It's basically in the same place for two days in a row," Carbin said. "That doesn't happen very often. Such rapid succession doesn't give any time for a break."
On Tuesday, the weather service sent survey teams to Vilonia, Ark., and nearby Garland County to investigate the damage and assess how much of it was caused by tornadoes or straight-line winds.