The National Weather Service warned of "impossible travel conditions" as the storm howls across the great plains, from Texas all the way to Montana and the Dakotas as it moves east.
Travel will be risky, if not impossible, at times, across the front range where the blizzard warning has been issued.
Meanwhile, thunderstorms were expected to keep pushing eastward Wednesday from the Southern Plains to the lower to middle Mississippi Valley.
The rain component of the storm, combined with very strong winds, creates the potential for damage to power lines and street flooding may occur in places where rain falls and drains have not been cleared, according to the weather service.
According to WPC, visibility will drop to near zero and "travel will become extremely risky".
Multiple Colorado school districtswere closed.
On Wednesday morning, some roads were already flooded in the northeastern part of Nebraska, and the National Weather Service issued a flood warning, saying more rain is expected later in the day.
Denver itself is expected to get snow accumulations of about 5 to 8 inches. More than 15 million are affected by a flood threat and about 10 million are under winter storm threats, according to CNN.
Wind gusts of 50 to 70 miles per hour are also expected to move through Colorado, New Mexico, Texas and Oklahoma this week, according to the NWS.
The storm is forecast to rapidly intensify overnight Wednesday east of the Colorado Rockies and trek slowly northeast through Thursday, bringing a variety of extreme weather from New Mexico to the Midwest. The storm is expected to wind down by Thursday evening, though residents should still take caution traveling in case of remaining wind, snow and floods.