A near-stationary front that has dumped more than a foot of rain across parts of Missouri, Illinois and Kentucky over the past four days pushed the Mississippi and Ohio rivers into major flood stage on Thursday, prompting mandatory evacuations in nine counties and the deployment of National Guard units in three states.

The National Weather Service’s Lower Mississippi River Forecast Center said gauges at Cairo, Illinois, the confluence of the two rivers, were expected to crest at 57.4 feet on Sunday — about four feet above major flood stage and the highest level recorded at the site since the 2019 spring inundation. Downstream gauges at New Madrid, Memphis and Helena were forecast to follow into early next week as the bulge of water moved south.

“This is the kind of event the river forecasters have been telling us was coming all month, and it has now arrived,” said Ken Graham, director of the National Weather Service, at a briefing from the agency’s headquarters in Silver Spring. “We have saturated soils, full reservoirs and a stalled boundary that is going to keep producing rain through Friday night. The window for people in the lowest-lying areas to move is closing.”

By midday Thursday, sheriff’s departments in Pulaski, Alexander and Mississippi counties in Illinois, and Mississippi, New Madrid and Pemiscot counties in Missouri, had ordered residents in floodplain neighborhoods to evacuate. Kentucky’s emergency management division added Ballard, Carlisle and Fulton counties to the list of mandatory zones late in the morning, citing rising backwater on the Ohio that was already cutting off rural roads west of Wickliffe.

Governor Beverly Andrade of Missouri, who declared a statewide emergency Wednesday evening, said at a news conference in Jefferson City that 1,800 National Guard troops had been mobilized and that the state had prepositioned 3.2 million sandbags along levees in the bootheel. “We are not going to wait for the river to tell us where to send help,” Andrade said. “We have been through this before, and the playbook works when we run it early.”

The four-day rainfall totals were extreme even by the standards of a region accustomed to spring deluges. A cooperative observer station at Cape Girardeau, Missouri, recorded 14.8 inches between Sunday evening and Thursday morning, the most ever measured there over any four-day stretch since records began in 1894. A gauge near Paducah, Kentucky, came in at 12.3 inches, and rural stations in southern Illinois reported isolated totals above 16 inches where training bands of thunderstorms had repeatedly crossed the same county lines.

Climate scientists pointed to a pattern that has become familiar in recent springs: a powerful low-level jet pulling deep Gulf of Mexico moisture northward into a stalled frontal boundary, with little upper-level steering flow to push the system along. “The atmosphere over the Lower Mississippi Valley right now is holding moisture at levels we would associate with late June, not the last week of April,” said Dr. Lena Voss, a climatologist with the Midwestern Regional Climate Center in Champaign. “When you couple that with soils that were already saturated from the early-April storms, almost every drop runs off into the rivers.”

The Army Corps of Engineers’ Memphis District said it had ordered controlled releases at three reservoirs in the upper Mississippi system to give downstream pools additional storage and was monitoring more than 600 miles of federal levee in the lower valley. Colonel Daniel Reyes, the district commander, said no levees had failed as of Thursday afternoon but that several were being watched closely for seepage. “The structures are doing what they were designed to do,” Reyes said. “Our concern is duration. If the river sits at crest for ten days, the math on these older sections gets harder.”

Flooding has already produced at least three confirmed deaths since the storm system organized over the central Plains on Sunday. The Missouri Highway Patrol said a driver was swept off a flooded county road near Sikeston on Tuesday evening, and a second person died after a tractor was overtaken by floodwaters in Stoddard County on Wednesday. In western Kentucky, a Graves County man drowned trying to retrieve livestock from a low-lying pasture on Wednesday night.

Agricultural impacts were beginning to come into focus. The U.S. Department of Agriculture said preliminary surveys showed that fields recently planted with corn and soybeans across roughly 1.8 million acres in the affected states were under water or expected to be by the weekend. “A two-week delay is recoverable for most growers, a four-week delay is not,” said Marcus Healy, an agricultural economist at the University of Illinois who has been tracking spring planting progress. Healy said replant decisions were going to dominate farm meetings across the region next week and that crop insurance claims would likely run into the hundreds of millions.

Barge traffic on both rivers was halted Wednesday by the Coast Guard, with closures running from St. Louis south to Greenville, Mississippi, and from Cincinnati west to the confluence. The American Waterways Operators trade group said roughly 1,400 barges were waiting at fleeting areas above and below the closures, with grain and fertilizer cargoes likely to face the longest delays. Officials at the Port of Memphis said it could be more than a week after the river crests before commercial traffic resumed in full.

Federal Emergency Management Agency Administrator Carla Mendez told reporters at the White House that incident management teams had been dispatched to operations centers in Jefferson City, Springfield and Frankfort, and that the agency was preparing to recommend that President Trump approve disaster declarations once state damage assessments came in. “We are leaning very far forward on this one,” Mendez said. “The forecast for the next 72 hours does not allow us to wait.”

Forecasters said additional rounds of heavy rain were possible across the same corridor on Friday before the front was finally expected to push east into the Tennessee Valley over the weekend. The Weather Prediction Center said an additional two to four inches was likely in already saturated areas, with locally higher amounts where afternoon thunderstorms developed along the boundary.

The National Weather Service said its next coordinated river forecast update, including revised crest projections at Memphis and below, would be issued Friday morning.