Flash Flood and Lightning Strike in Iowa, August 7, 1999

An east to west warm front was poised along the southern Iowa border as a weak surface wave advanced east along the frontal boundary. Low level winds increased to nearly 40 kts during the night, transporting moist and unstable air over the frontal boundary. Surface dew point temperatures were in the low to mid 70s south of the front with precipitable water values near 50 mm. Upper level winds were fairly strong from the west. An MCS formed during the previous night and advanced across Nebraska into western Iowa during the day. As the night progressed, the MCS became a full fledged MCC as it back developed over southwest Iowa. Intense rainfall fell just to the west of the Des Moines CWA with estimates in excess of a foot of rain and the highest official total in Omaha with 10.48 inches recorded at Eppley Field. An unofficial total of 15 inches was received from Montgomery County in the town of Wales. Rainfall of 4 to 6 inches occurred over southwest Cass County, causing flash flooding in the Griswold and Lyman areas. Numerous streets and highways were under water for a few hours, however this was not a major event in that area. As the storms moved east across south central Iowa, lightning struck a tree in the town of Leon in Decatur County. Half of the tree fell onto a house there and pieces of the tree were blown up to a block away.