About 1,100 motorists were stranded in Colorado as a ferocious winter storm -- a "bomb cyclone" -- unleashed hurricane-force winds and blizzard conditions in parts of the central United States.
"We are in full saving lives mode," said Ryan Parsell, a spokesman for El Paso County, about the ongoing rescues. "This isn't your average Colorado storm."
The weather has been so severe in the state that law enforcement officers had to abandon their vehicles and get shelter themselves instead of responding to the high volume of motor vehicle accidents, officials said.
"We are at the point where we are rescuing rescuers out there," said Elbert County Manager Sam Albrecht.
In Weld County, north of Denver, State Patrol Cpl. Daniel Groves, 52, was struck by a car Wednesday morning while assisting a motorist whose car slid off Interstate 76, according to the state police. Groves, on the job since 2007, was declared dead at a hospital.
High speed in poor driving conditions was being investigated as a possible factor, the patrol said. No charges had been filed.
The storm morphed into a "bomb cyclone" Wednesday and roared through Colorado on its way to the Great Plains and parts of the Midwest.
A bomb cyclone happens when there's a rapid pressure drop, with a decrease of at least 24 millibars (which measures atmospheric pressure) over 24 hours known as bombogenesis. This storm has dropped 33 millibars since Tuesday morning and continues to strengthen.
The storm is bringing hurricane winds to the Rockies and as far away as Amarillo, Texas. Winds gusts equivalent to Category 1 and 2 hurricane winds were reported at the Denver International Airport and in Colorado Springs, the National Weather Service.
In New Mexico, heavy winds contributed to the derailment of a 26-car train near the village of Logan, according to a tweet from state police. No injuries were reported.
Storm has left thousands in the dark
In Colorado, at least 184,000 Xcel Energy customers were affected by weather-related power outages, company spokeswoman Michelle Aguayo said. Nearly 5,000 people with other utility companies were also without power, officials said.
In Texas, more than 69,000 people had no power, according to Jen Myers, spokeswoman for provider Oncor. Myers said the sudden wind gusts hit the state with unusual force.
"We're pretty used to seeing Texas storms knock out power, but they tend to be localized," she said. "This was a very widespread event. Everybody's out working to restore power, and all of our crews are out in full force to make sure we can get the power on as soon as possible."
Thousands of power outages were reported in the Denver area alone.
Blizzard blasts Colorado
The massive storm was walloping the Rockies. By early afternoon, more than 9 inches of snow had been reported west of Boulder, Colorado, and winds gusting above 50 mph were whipping through central portions of the state.
"And yes, that is the equivalent of a Category 1 hurricane! This is a serious blizzard! DO NOT EVEN ATTEMPT TO DRIVE IN THIS STORM!" the weather service's office in Boulder said on Twitter.
The storm is on its way to the central and northern Plains and the Upper Midwest with blizzard conditions. Hazards include heavy snow and severe storms with possible tornadoes and flooding into Thursday.
Blizzard and winter storm warnings are in effect for portions of Colorado, Wyoming, Nebraska and South Dakota.
Watches, warnings and advisories for the storm cover about 1.5 million square miles, which is roughly half of the area of the continental United States -- and they stretch from the Mexican border to the Canadian border.
Travel will be dangerous, if not impossible, at times, across areas where the blizzard warning has been issued. Severe storms capable of producing damaging winds, hail, and tornadoes are forecast from the southern Plains and into the Mississippi River Valley. More than 55 people million are under a high wind threat; more than 10 million are under winter storm threats; and more than 17 million are under a flood threat.
Travel and schools affected
More than 2,000 US flights had been canceled by Wednesday night, according to FlightAware. The majority of those cancellations were flights destined for or originating at Denver International Airport (DIA), where a blizzard warning is in effect.
Denver itself is expected to get snow accumulations of about 5 to 8 inches.
Multiple Colorado school districts were closed. That includes Denver Public Schools, which cited "severe weather and road conditions."
Wyoming had closed state offices in Cheyenne, while South Dakota's governor ordered state offices closed in 39 central and western counties because of the storm.
In Nebraska, officials closed a roughly 130-mile stretch of westbound Interstate 80, from Ogallala to the state line with Wyoming, because of the blizzard.
Thunderstorms across portions of the southern Plains will make way for sustained winds of 35 to 45 mph, akin to the strength of a low-end tropical storm.
Storm set to intensify overnight
Wind gusts of 50 to 70 mph are expected through Thursday morning across Colorado, New Mexico, Texas and Oklahoma, CNN meteorologist Monica Garrett said. Some areas could see gusts as strong as 110 mph.
The storm is forecast to rapidly intensify overnight east of the Colorado Rockies and trek slowly northeast through Thursday, bringing a variety of extreme weather from New Mexico to the Midwest. Snow is expected to taper off by midday Thursday, but strong winds may persist through the evening.
In addition, flood watches have been issued across the Midwest and Great Plains amid concerns that heavy rains will melt snowpack and trigger significant flooding. Flash flooding is possible if ice jams clog rivers and streams, the weather service noted.
By Nicole Chavez, Allie Mazurek and Judson Jones, CNN