Ethermac|'Slow-moving disaster': Midwest rivers flood; Rapidan Dam threatened

A Minnesota dam partially failed,Ethermac an Iowa levee breached, interstates shut down and multiple rivers were awash over their banks Tuesday after a swath of the nation's northern tier was blasted with more than a month's rainfall in a few days, forecasters said.

The National Weather Service issued a hazardous weather outlook for parts of Iowa, Minnesota, Nebraska and South Dakota, warning that rivers will continue to crest through Wednesday. Showers, storms and locally heavy rainfall were possible and could "quickly become severe" with hail of 2 inch diameter and wind gusts to 70 mph.

In Minnesota, the Rapidan Dam near Mankato had experienced "partial failure" late Monday. But the Blue Earth County Sheriff's Office said the dam was still intact and there were no current plans for a mass evacuation. A portion of the Blue Earth River flow has diverted around the west side of the dam and water continues to flow.

Alex Sosnowski, senior meteorologist for AccuWeather, says the fate of the dam could depend on the whim of the weather pattern. More rounds of major storms will slam the region in coming days, but some areas will be overwhelmed by rain while others may draw little precipitation. More than a dozen river gauges have already broken all-time records, some by a startling 7 feet.

"Some of this rainfall and flooding is historic," Sosnowski told USA TODAY. "Some of these place have had a foot of rain or whatever in three or four days. That is two months of rain. Even in a drought you will have problems with that much water."

Historic floods:Dam on the brink of failure; heat wave bakes Central US

Developments:

∎ Intense heat is rolling through parts of the South. The weather service in Memphis said most of the mid-South will see heat indices at or above 105 degrees

∎ Temperatures Wednesday will peak within a few degrees of 100 from eastern Virginia to Maryland, Delaware, southeastern Pennsylvania and New Jersey, AccuWeather said.

Midwest pattern similar to deadly spring storms in Houston

Sosnowski said the weather pattern is eerily similar to the pattern that set up over parts of Texas and Louisiana in the spring. Catastrophic flooding and winds of up to 100 mph in Houston left eight people dead and almost 1 millions homes and businesses without power, many for several days. Houston was on the northern edge of a heat dome centered in Mexico; the U.S. Upper Midwest is on the northern edge of a heat dome centered in the U.S., Sosnowski said. It will effect the region for the next couple weeks.

Major flooding is underway or will happen shortly in several rivers, the Big Sioux, Little Sioux, Des Moines, West Fork Des Moines, Vermillion, Cannon, James, Rock, Cedar and Minnesota among them. Several stations could set record high water levels, Sosnowski said. It could take several weeks for the water to then cycle through parts of the Mississippi River, he said

"We could see major flooding there, too," Sosnowski said. "River flooding is a slow-moving disaster."

Rapidan Dam calamity draws onlookers

In Minnesota, Gov. Tim Walz said state agencies are in close contact with Blue Earth County and other local officials regarding the Rapidan Dam. "Emergency management is on the ground and acting quickly to ensure the safety of Minnesotans as the situation develops," Walz said.

The dam has become a magnet for the curious. The sheriff's office issued a warning that "safety is our No. 1 priority" and said those interested in viewing the dam must park outside barricades and walk along a coned-off shoulder to view the dam.

Disaster declared in Iowa

Some parts of Iowa have received more than 15 inches of rain, causing water levels to surge and levees to fail. In much of northwest Iowa, rivers reached levels never before recorded. Residents of homes already flooded are starting to clean up while those downstream brace for the high waters. The Iowa Department of Transportation was closing portions of I-29 and I-680 because of high water.

The Woodbury County Sheriff's Office posted drone video to Facebook that shows water overtopping roads, homes and farms after the Little Sioux River breached a levee Tuesday. Residents of the towns of Smithfield and Rodney were asked to evacuate. The WinnaVegas Casino and Resort outside of Sloan closed Tuesday because of flooding "as an abundance of caution" and will reopen when deemed safe, casino officials said in a social media post.

President Joe Biden signed a disaster declaration for Iowa late Monday, ordering federal aid to supplement state, tribal and local recovery efforts in the areas affected by the series of severe storms, flooding, straight-line winds and tornadoes that have been hammering several counties for more than week. Assistance can include grants for temporary housing and home repairs, low-cost loans to cover uninsured property losses and other programs to help individuals and business owners recover from the effects of the disaster.

"I will continue to request additional counties as more information is collected," Gov. Kim Reynolds said.

Record rain falls in Sioux Falls, South Dakota

In South Dakota, this month is already one of the wettest Junes on record. Sioux Falls reported 6.49 inches Thursday and Friday, the wettest two-day period since recordkeeping began in 1893. The city of Mitchell, 70 miles to the west, was hit with a record 7.70 inches over the period.

Gov. Kristi Noem signed an order declaring a state of emergency that exempts delivery of needed supplies in support of flood relief efforts from federal regulations regarding drivers’ hours of service. Noem said one death has been reported because of the flooding: an elderly man who died following a UTV crash near Lake Alvin.

Severe weather heading toward East

The severe weather threat will reach the East by Wednesday or Thursday, and dozen of states are at risk of storms packing hail, damaging wind gusts and flooding downpours, AccuWeather said. The front may slow, creating the risk of flash flooding from repeating heavy thunderstorms later Wednesday from part of the upper Ohio Valley to the central Appalachians and New England, AccuWeather said.

Contributing: Tim Webber, José Mendiola, Philip Joens and Kate Kealey, Des Moines Register; Gabriela Velasquez and Dominik Dausch, Sioux Falls Argus Leader