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By Kalhan Rosenblatt and Phil Helsel

Thousands of Coloradans woke up in the dark Thursday after a winter storm system pounding the central U.S. knocked down power lines, grounded flights and buried highways in snow.

As many as 74 million people were expected to face some type of severe weather ranging from blizzard conditions to heavy rain and flooding through Friday.

Colorado Gov. Jared Polis declared a state of emergency Wednesday and tweeted that the National Guard had been activated to assist in search and rescue and other operations.

Authorities said 1,100 motorists were "stuck and stranded" in "treacherous conditions" on roads in Colorado's El Paso County. Sheriff Bill Elder added that search and rescue operations would continue through the night. His advice was to "STAY HOME."

Around 86,000 customers in Colorado were without electricity early Thursday, according to Xcel Energy. Another 47,000 had no power in New Mexico and northern Texas.

The storm underwent bombogenesis — also known as a bomb cyclone — according to The Denver Post, a term used when a storm drops 24 millibars, or units of atmospheric pressure, in 24 hours or less, according to Weather.com.

It has contributed to at least one death. A Colorado State Patrol officer, Cpl. Daniel Groves, 52, was killed Wednesday after he was struck by a vehicle on Interstate 76 while responding to another vehicle that slid off the road.

The patrol said in a statement that "high speed in poor driving conditions is being investigated as a possible causal factor," but the incident was under investigation and no charges have been filed.

Denver International Airport's runways were shut down Wednesday, and almost 1,400 flights were canceled amid the whiteout, the Denver Post reported. The newspaper noted that it was only the fourth time in the airport's history that runways had been closed.

More than 5 inches of snow was recorded at the airport as of 5 p.m. Wednesday, while parts of Colorado Springs and Aurora reported 10 inches, according to the weather service.

Denver remained under a blizzard warning through midnight with as much as a foot of snow in the forecast. The state Department of Transportation closed stretches of interstates 25 and 70 until at least Thursday morning due to blizzard conditions, and other highways were also closed, NBC affiliate KUSA of Denver reported.

Blizzard warnings stretched on a large swath of the central U.S., from eastern Colorado and Wyoming, portions of Nebraska and large parts of the Dakotas and into western Minnesota as of Wednesday night, while eastern Nebraska, southeastern South Dakota and parts of Iowa were under flood warnings.

Between 6 to 12 inches of snow is likely for the central and northern plains through Thursday, particularly in the central portions of the Dakotas, the weather service said in a forecast discussion.

The Nebraska Department of Transportation warned that residents could face flooding and blizzard conditions into Thursday.

It wasn't just the snow causing disruptions. In New Mexico, the storm's high winds derailed a train on Wednesday, according to state police.

Severe thunderstorm warnings also stretched from southwestern Texas to parts of Kansas, according to the weather service. Parts of Wisconsin and Michigan were among the areas under a flash flood watch.

In Texas, Dallas-Fort Worth recorded gusts of wind between 75 mph and 78 mph early Wednesday.

Dallas/Fort Worth International Airport had several jet bridges damaged in Wednesday's storm, and there were cancellations and a number of flight delays, an airport spokesperson said. The terminals were not damaged.

In Tennessee and parts of Mississippi, as much as 4 inches of rain could fall through Friday.

Linda Givetash and Kurt Chirbas contributed.