Erikson said the flooding “could be worse than anything we have seen in recent years,” including the devastating floods in 1993 and 2011, considered among the worst in U.S. history.
Due to rivers levels that are already high, hefty snowpack in the northern plains and above-normal soil moisture, “conditions are primed” for more flooding, said Edward Clark, director of NOAA’s National Water Center. “This is potentially an unprecedented flood season,” Clark said. “It may become more dire in the coming weeks.”
The outlook said 200 million Americans are at risk of experiencing flooding.
“The areas of greatest risk for moderate to major flooding include the upper, middle, and lower Mississippi River basins including the mainstem Mississippi River, Red River of the North, the Great Lakes, eastern Missouri River, lower Ohio, lower Cumberland, and Tennessee River basins,” the outlook said.
Major flooding causes “extensive inundation of structures and roads,” according to the National Weather Service, and frequently requires evacuation of low-lying areas.
The flood damage over the past week has cost $1.3 billion in Nebraska alone and has caused at least four deaths.
The Weather Service’s Erikson described flooding as an “underrated killer” that leads to nearly 100 deaths in an average year.
Clark said about two-thirds of the Lower 48 is likely to experience some flooding this spring. Even away from the zone of greatest risk in the nation’s heartland, minor flooding, which can inundate roads and basements, remains a risk east of the Mississippi River and in parts of California and Nevada, the outlook noted.
NOAA’s Climate Prediction Center favors above normal precipitation during the April to June period over much of the nation’s middle, which will compound the flood risk. This follows a winter in which record precipitation fell in parts of the north central United States, in some places 200 percent of normal.
The United States overall had its wettest winter in recorded history.
But perhaps a bigger threat than any precipitation in the pipeline is the water locked in the snowpack. In the eastern Dakotas and most of Minnesota, more than 20 inches of snow remains on the ground.
Over the next week, computer model simulations show that snowpack eroding, which will release large quantities of water into river systems, intensifying flooding and ice jams.
As of Thursday, over 100 river and stream gauges in the central United States indicated moderate to major flooding, and another 140 indicated minor flooding. “The extensive flooding we’ve seen in the past two weeks will continue through May . . . and may be exacerbated in the coming weeks as the water flows downstream,” said Clark.