A tornado touched down near McCook shortly after 6 p.m. Friday, the National Weather Service said.
Social media posts and photos indicated the tornado was moving through open fields. There were no reports of damage as of 6:20 p.m.
The tornado, which touched down at 6:02 p.m., was located about 9 miles northeast of Culbertson and 9 miles northwest of McCook. It was moving north at 45 mph and was expected to be near Curtis at 6:35 p.m.
Severe weather was moving across much of north-central Nebraska Friday afternoon, including a series of thunderstorms and golf-ball size hail.
Severe thunderstorms had moved into the area of Rock, Brown, Boyd and Keya Paha Counties, according to Brandon Thorne, a National Weather Service meteorologist in North Platte. The area received hail ranging in size from a quarter to a golf ball beginning sometime after 3 p.m. he said.
A tornado warning was in effect for western Frontier County until 6:45 p.m.