Heavy rain caused flooding in eastern parts of both states, as well as in Iowa. According to the National Weather Service, areas like Dallas and Colorado are now the most affected, but wider estimates predict that millions of Americans across the central region could be directly hit in the next few days.
South Dakota Gov. Kristi Noem closed all state offices Thursday as the blizzard conditions moved in, and later in the day ordered the opening of the state's Emergency Operations Center to handle the response to the blizzard and flooding. "The positive spin on this, if you want to put it that way, is there was so much energy focused with this storm, if you look at the usual tornado outbreaks that occur with these big storms that go up into the plains - very minimal overall".
The Colorado State Patrol said one of its troopers, 52-year-old Corporal Daniel Groves, was killed northeast of Denver when a vehicle veered out of control and struck him as he was helping the victims of another auto accident.
The blizzard, bringing severe snowfall, poor visibility and powerful winds, caused hundreds of flight cancellations and thousands of power outages in Colorado and Texas. Some 85,000 people, mostly in the Denver area, were still without electricity Thursday.
"It caught me completely off guard", said Sarah Brin of Santa Fe, New Mexico, who was stranded at the Denver airport.
Weather.com also reported blizzard warnings being issued in parts of eastern Wyoming, southeastern Montana, western Nebraska, western and central South Dakota, central and eastern North Dakota and northwest Minnesota.
"Travel will remain hard and life threatening across these areas, with improving conditions Thursday night into Friday as the storm pushes farther off to the northeast", the NWS says. Missouri, Mississippi, Nebraska, Wisconsin (bottom left), and Iowa are already drenched in massive floods.
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"We do know that here is a link between the warming Arctic and the weather patterns in the mid-latitudes", she said. The Red Cross opened shelters in Sioux Falls and Yankton.
A wind gust of 92 miles per hour (148 kph) was recorded in the mountains northwest of Denver. Officials with the Colorado National Guard and state police said they believed all stranded motorists had been rescued overnight, but searches were ongoing Thursday. A dairy euthanized about 150 cows injured by the tornado.
A mountain wave is an area of extremely turbulent air found on the lee side of a mountain barrier like the Rockies when there is a strong flow of wind present.
An AccuWeather meteorologist said on Thursday on Twitter that at least one tornado had formed near Evansville, Indiana.
"It's like a vacuum cleaner, really", Carbin said.
The wind also contributed to a 26 vehicle train derailment in New Mexico, CNN reported.
Meteorologists call storms like this one a "bomb cyclone", a winter hurricane that forms when the barometric pressure drops 24 millibars in 24 hours. Air rushed into the low-pressure area and then rose into the atmosphere, causing severe weather.