Heavy rain has been affecting portions of Louisiana and Mississippi recently. The rainfall has been associated with a deepening, slow-moving area of low pressure drawing in plentiful Gulf of Mexico moisture. That has led to some totals around and exceeding 24". As a result, there have been well over 1,000 water rescues and two fatalities. The situation likely won't improve for a few days with a stalled out stationary boundary set up through the Mississippi Valley area. That front, combined with low pressure, will continue to support an active pattern with heavy rain in the forecast from New Orleans to Memphis to Cincinnati into early next week.
In fact, an additional 5-9" or more of rainfall is expected in parts of Louisiana, Arkansas, Missouri, southern Illinois, Kentucky, and southern Indiana. That will aggravate the already saturated ground in those locations, which will lead to a significant flooding concern from the Gulf of Mexico northward to the Ohio River. In Louisiana, some rivers will crest more than four feet above their respective record crest. For northern Illinois and southern Wisconsin, low pressure will remain just far enough south into early next week to keep mainly dry weather in the forecast. A few isolated showers are possible Monday, Tuesday, Wednesday, and Thursday, but the concentrated rainfall will remain along and south of a St. Louis to Champaign-Urbana to Indianapolis line.