Just eight days after a deadly tornado struck southwestern Indiana, emergency warning sirens wailed Tuesday morning as a storm system produced at least one funnel cloud.

The National Weather Service issued tornado warnings for the Evansville area and an adjacent section of Illinois. Flood warnings also were posted as more than 6 inches of rain fell in parts of the Ohio River Valley.

"We have a funnel cloud spotted in Posey County, but we don't actually have anything on the ground," said Ryan Presley, a weather service meteorologist in Paducah, Ky.

Meteorologists said a cold front moving eastward and colliding with warm, unstable air was producing severe thunderstorms in the region.

Dan Spaeth, a weather service forecaster, said the conditions were similar to those that produced the tornado on Nov. 6 that caused 41 miles of damage and killed 23 people.

The most severe damage on Nov. 6 was in a mobile home park on the eastern edge of Evansville where 19 of the victims were killed. Four other people were killed in neighboring Warrick County.

Elsewhere in the Midwest, nine tornadoes swept across central Iowa on Saturday, killing one woman.

Though severe thunderstorms and tornados are not uncommon in the fall, Spaeth said the strength of storm systems that have produced recent tornadoes suggests severe weather ahead.

"It's not usually as widespread or frequent," he said. "But if it happens once, it can happen again."