Flooding in Iowa, June 13 to 17, 2000

Northeast Iowa was again the recipient of heavy rainfall during the early morning hours of June 13, as a mesoscale convective system developed along the 850 mb warm front being fed by a strong low level jet. Surface dewpoints were around 70 degrees F in the air that was being pushed across the boundary. WSR-88D radar estimates were three to four inches in parts of the Cedar River Basin, especially in the subbasin above Janesville. Despite this, the river did not reach flood stage. A very moist and unstable air mass remained in place over most of Iowa during the day on the 13th and thunderstorms began redeveloping around mid morning. Many of the ingredients for strong storms were in place, including precipitable water up to two inches, CAPE values of 4000 J/kg, and lifted indices of -10 C. or below over southwest Iowa. Two distinct periods of rainfall affected the area on the 13th. late morning maxima was centered over northeast Iowa, with another over southern Iowa. Numerous urban and small stream flood advisories were issued. These included Humboldt, Polk, Warren, and Franklin Counties. One to two inches of rain fell over Des Moines in several hours, causing some urban street flooding but no serious impacts. Amounts were heavier in the other counties with as much as four to six inches over parts of Franklin County. In spite of these rains, flooding impacts were minimal. The widespread rains caused substantial rises on rivers in northeast Iowa, including the Iowa, Beaver Creek, Shell Rock, Cedar, and West Fork Cedar Rivers. All of the flooding was comparatively minor, with most of it limited to agricultural flooding.