A sudden drop in barometric pressure unleashed a rare "bomb cyclone" over the US state of Colorado, paralysing the region with heavy snow and high winds.
According to the National Weather Service (NWS), as many as 74 million Americans could be affected by the storm, which hit southern Colorado with Category 2 hurricane conditions on Wednesday and 100 mile per hour winds, Xinhua news agency reported.
A late-winter blizzard slammed US Rocky Mountain and Plains states on Wednesday, unleashing a "bomb cyclone" of high winds and drifting snow that stranded motorists, cancelled more than 1,300 airline flights and was blamed for the death of a Colorado state trooper.
More than 55 million people are "threatened" by high winds, 10 million by winter storms and over 17 million by floods, with "severe storms capable of producing damaging winds, hail and tornadoes, the NWS said.
Thousands of cars were abandoned along the Colorado roadways as "the bomb cyclone wreaked havoc, triggering innumerable crashes and leaving people stranded in cars", the Denver Post reported.