While floodwaters may have receded in parts of the Midwest that have been inundated since the "bomb cyclone" triggered a devastating deluge earlier this month, forecasters are warning that snowmelt and heavy spring rains are creating the threat for major flooding through May.

The National Oceanic and Atmospheric Administration released its spring outlook on Thursday, stating that nearly two-thirds of the lower 48 states face an elevated risk of flooding through May, with the potential for major or moderate flooding in 25 states.

“The extensive flooding we’ve seen in the past two weeks will continue through May and become more dire and may be exacerbated in the coming weeks as the water flows downstream,” said Ed Clark, director of NOAA’s National Water Center in Tuscaloosa, Ala. “This is shaping up to be a potentially unprecedented flood season, with more than 200 million people at risk for flooding in their communities.”

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The upper Mississippi and Missouri River basins in states such as Nebraska, Minnesota and Iowa have already been facing devastating flooding this year after rapid snowmelt combined with heavy spring rain.

Thousands were forced from their homes in Nebraska, Iowa, and Missouri, as water broke through or poured over levees in the region. The damage is estimated at $3 billion, and that figure is expected to rise.

"Additional spring rain and melting snow will prolong and expand flooding, especially in the central and southern U.S. As this excess water flows downstream through the river basins, the flood threat will become worse and geographically more widespread," the NOAA said.

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Record precipitation over the winter has set the stage for an elevated flood risk along the upper, middle and lower Mississippi River basins including the Mississippi River. The threat also exists along the Red River, the Great Lakes, eastern Missouri River, lower Ohio, lower Cumberland and Tennessee River basins.

Snowmelt in the Dakotas and Minnesota is expected to send more water down those rivers, and above-average precipitation is also expected over the Central and Eastern U.S., adding to the flood risk.

"The upper Mississippi and Red River of the North basins have received widespread rain and snow this spring, up to 200 percent of normal," National Weather Service Deputy Director Mary Erickson told reporters.

The agency's flood risk outlook is based on several conditions, including snowpack, drought, soil moisture, frost depth and precipitation.

"Local heavy rainfall, especially associated with thunderstorms, can occur throughout the spring and lead to flooding even in areas where overall risk is considered low," the agency said. "In the western U.S., snowpacks at higher elevations may continue to build over the next month, and the flood risk will depend on future precipitation and temperatures."

On Saturday, Iowa Gov. Kim Reynolds said President Trump granted her request for an expedited disaster declaration for 56 counties with flooding damage. The move makes assistance available to homeowners, renters, businesses, public entities and some nonprofit organizations. Flooding in Nebraska has caused an estimated $1.4 billion in damage. The state received Trump's federal disaster assistance approval on Thursday.

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In Missouri, a precautionary evacuation involving hundreds of homes in the St. Joseph area was lifted Saturday as the Missouri River began a swift decline after unofficially rising to a new all-time high, inches above the 1993 record.

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The Missouri River had yet to crest further downstream in Missouri, but the flooding impact in those areas was expected to be far less severe.

St. Joseph was largely spared, but Buchanan County Emergency Management Coordinator Bill Brinton told the Associated Press that 250 homes were flooded in the southern part of the county. It wasn't clear when residents would be able to get back, but Brinton said the region has already been ravaged by flooding this year.

"There's a sense from the National Weather Service that we should expect it to continue to happen into May," Brinton said. "With our levee breaches in Atchison and Holt and Buchanan counties, it's kind of scary, really."

The Associated Press contributed to this report.