2007 Midwest Flooding - Meteorological Synopsis

Meteorological Synopsis

On Saturday, August 18, a warm front pushed northward into Iowa and Illinois, where it became stationary. Warm, moist air pushing over the frontal boundary fueled showers and thunderstorms that moved in a west-to-east fashion, training over the same areas for hours at a time. Some parts of Minnesota, Wisconsin and Iowa saw moderate to heavy rain for nearly a full day before the activity finally cleared out. Additional thunderstorms formed over these areas on Sunday, August 19, exacerbating the flooding problems. Tropical Storm Erin had pushed into the coast of Texas on August 15, and by August 18 had stalled over Oklahoma. Though the remnants of Erin did not directly impact the flooding in these areas, moisture from Erin streamed northward, enhancing the thunderstorm activity for two to three days.

The stationary front and associated energy then extended eastward through Illinois, Indiana and Ohio on August 19 and August 20. Similarly, the front was the focus for thunderstorm development, and the precipitation continued moving over the same areas, leading to extended periods of heavy rainfall. Approximately 1,000,000 homes lost electricity due to the storms.

Runoff from the heavy rain also caused river flooding to the south of the affected areas. The Rock River near Joslin, Illinois peaked at 17.11 feet, 5.11 feet (1.56 m) above flood stage. Moderate flooding was also reported on the Mississippi River from the Quad Cities to St. Louis, Missouri.