Cpl. Daniel Groves, 52, was assisting a vehicle that slid off Interstate 76 in Weld County when someone driving a Volvo "lost control" and hit Groves, who was outside of his patrol vehicle, Colorado State Patrol said on Twitter.
Groves was transported to the hospital, where he was pronounced dead.
The driver who allegedly hit Groves, 58-year-old John Carpenter, was also transported to the hospital with moderate injuries, officials said.
The National Weather Service had issued a blizzard warning for Weld County and surrounding areas in eastern Colorado on Wednesday. Authorities are investigating "high speed in poor driving conditions" as a possible cause of the accident.
Groves had worked with the Colorado State Patrol since July 2007, according to the department.