This storm of epic proportions has been dumping heavy amounts of rain and snow, leaving tens of thousands without electricity and causing the death of a police officer in Colorado.
The quickly rising floods evacuated people from their homes, washed out roads in communities, and left farmers anxious all the water would drown livestock. The state was preparing an emergency declaration, Noem said.
In Sioux Falls, S.D., the eponymous falls were raging Wednesday and Thursday, and floodwaters forced dozens of road closures. The flooding was the worst in almost a decade in places, though the situation was expected to improve quickly in many places over the weekend, according to Mike Gillispie, National Weather Service hydrologist in Sioux Falls.
"We've got a lot of water, and it's got to find a way to get out of here", said Tracy West, mayor of Lennox, South Dakota.
The "bomb cyclone" late winter storm is swirling eastwards after wreaking havoc in western states. A wind gust clocked in at 97 miles per hour (156 kph) in Colorado Springs.
"Just today we're facing blizzards, white-out conditions, flooding, dense fog, and each of those pose a unique risk", he said.
The National Weather Service says the system is expected to move into southern Minnesota and parts of IL, including Chicago, on Friday, with rain later turning to snow.
The culprit was a sudden and severe drop in ground-level air pressure in Colorado, the most pronounced dive since 1950 and something "that will go down in the history books", said Greg Carbin, chief of forecast operations for the National Oceanic and Atmospheric Administration's Weather Prediction Center.
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A bomb cyclone occurs when there is a rapid pressure drop that occurs over the course of 24 hours.
"The intensity of this storm is due to a merging of two powerful jet stream disturbances that created a strong area of low pressure next to an area of high pressure that is feeding mild air and moisture from the Gulf of Mexico northward", Aggarwal said.
Such severe conditions have led to the closing of school districts in areas of Colorado, with power being unavailable to over 175,000 people.
As authorities scrambled to rescue drivers, Colorado State Patrol Corporal Daniel Groves was killed after being struck by a vehicle while helping a stranded driver.
The Colorado National Guard announced it had rescued 93 people and two dogs after inspecting about 250 vehicles.
The window-rattling storm brought blizzards, floods and a tornado across more than 25 states Wednesday, stretching from the northern Rocky Mountains to Texas and beyond.
Five people were hurt and 150 dairy cows had to be euthanized when a tornado hit the small town of Dexter, New Mexico, on Tuesday. There are no immediate reports of any injuries, but homes and trees were damaged and power was knocked out to thousands. "There's only been three or four tornadoes reported here".
More than 105 million people were affected by the storm system, the National Weather Service said Thursday.