Floodwaters covered highways from Arkansas to Ohio. Schools in waterlogged communities called off Friday classes. And river towns across the South and Midwest piled up sandbags ahead of a weekend when forecasters expect intense rain and major floods.

The preparations for heavy flooding intensified on Thursday following an outbreak of tornadoes and heavy winds overnight. The storm leveled homes and businesses and killed at least seven people in three states, including a fire chief in Missouri and a teenage girl in Tennessee. At least two offices of the National Weather Service have said they are delaying or skipping sending staff into the field to survey damage from this week’s severe weather, a key step that meteorologists usually use to confirm whether or not a tornado has struck.

On Wednesday night, the Weather Service office in Louisville, Ky., said in a statement to local news organizations that it would be unable to do storm surveys because of the active threat of severe weather, a concern that was echoed on Thursday by Justin Gibbs, the meteorologist in charge of the Paducah, Ky., office, who said the ongoing rain and flooding would slow down the survey process. McNairy County in Tennessee, one of the hardest-hit areas of the state and where at least one person has been killed by the storms, is experiencing “widespread communications issues,” the Tennessee Emergency Management Agency said in a statement. The officials said that several inches of rain and damaging winds continue to threaten western Tennessee, including McNairy County, through the end of Thursday and potentially on Saturday.