A slow moving storm system will bring another prolonged period of rain to central Illinois toward the end of the week. With the ground already saturated from recent and ongoing rain, and many rivers already in flood, the expected rainfall will bring a rather widespread threat of flooding.
Plenty of warm and moist air will be in place over the region, as a very slow moving storm system moves into the Midwest on Thursday. These muggy conditions will provide plenty of moisture for a series of upper level disturbances that will move along the boundary. As a result, extensive showers and thunderstorms are expected to produce copious amounts of rain along and near the boundary. In addition, this boundary will become nearly stationary as it moves into the region. Computer model solutions vary somewhat, with the exact position of the front still uncertain, but they agree in widespread rainfall from Thursday through Saturday. The rainfall forecast from the NWS Weather Prediction Center (shown below) shows the potential for widespread 3 to 5 inch amounts over much of central Illinois, with even higher totals across southern Iowa and northern Missouri. This amount of rain would cause even further rises on area rivers; the Illinois and Spoon Rivers are currently in flood, and more rivers would see flooding develop in this scenario. Monitor river forecasts on our Advanced Hydrologic Prediction Service page.