Extremely heavy rain fell across southern Minnesota into central Wisconsin Wednesday night and Thursday, with record September rainfall at some locations. Amounts of 3 to 5 inches fell in a broad band, with a narrow band of 6 to 10 inches. This water coming downstream may cause flooding on the Mississippi River within a week. Below is an image of the heavy rainfall amounts reported as of Thursday afternoon.
The tricky part for forecasting what the crest will be is that the rainfall will enter the MIssissippi at different times through the following tributary rivers: the Minnesota, Wisconsin, Wapsipinicon, Cedar, Iowa, and Des Moines. As water from each tributary is added to the Mississippi the flood crest will lower somewhat due to the water backing up into the smaller tributaries as the flood crest moves downstream.
Flood warnings may eventually be needed for the Mississippi River and if so will be issued over the next several days. Current projections indicate flood stage could be reached sometime next week depending upon the location on the river.
Individuals with interests along the Mississippi can expect crest forecasts to change considerably over the next several days and you should continue to monitor this situation, especially if flood warnings are issued.