One of the multiple flood warnings and watches from the National Weather Service over Aug. 9-10 was for areal flooding. What is it?

MILWAUKEE (AP) — The Milwaukee area began drying out Monday after weekend rain hit unofficial state records of more than 14 inches (36 centimeters) in less than 24 hours, leading multiple rivers to flood at record-high levels, washing out vehicles, flooding basements and cutting power to thousands of homes.

A slow-moving storm system that battered Wisconsin over the weekend prompted flood advisories in several states across the central U.S.