Heavy thunderstorms and tornadoes crimped cleanup efforts yesterday by Iowa and South Dakota residents still reeling from weekend weather, and Nebraska reported its first fatality from recent floods.

After morning rains added 1 to 2 inches to watersheds of flooded rivers, Iowa Gov. Terry E. Branstad (R) added 11 counties to 22 already declared disaster areas. That brings the total to one-third of the state's 99 counties.

The National Weather Service said no appreciable additional flooding was expected. Three deaths in Iowa have been blamed on the most recent storms.

Police in Des Moines asked employers to send workers home early because storm sewers had backed up, clogging major streets leading out of downtown.

In the central Iowa town of Jewell, about 55 miles north of Des Moines, a tornado ripped the roof off of South Hamilton High School. Another tornado was reported just north of there in Webster City.

"Two months ago, we were concerned about the drought and now here we are faced with major flooding," Branstad said, adding that agricultural damage could be severe unless flood waters recede soon. "There's a considerable amount that's been flooded, and it's getting very late as far as replanting," he said.

A 77-year-old West Point, Neb., man was found drowned, apparently the first person to die in flood waters that have plagued northeast Nebraska for nearly a week. A relative found the body 1 1/2 blocks from the man's home, about 2 miles south of West Point near the Elkhorn River.

More storms ravaged south-central and northeastern Nebraska on Monday night. Flooding also was reported in Pennsylvania.