I'm guessing it was a double stack or auto rack train as they would be more reflective of the weather radar signal than a merchandise train (boxcars). A rough estimate of the speed would be 60-70 mph which is approximately correct if a train was getting "clear" signals. The train would be on the UPRR's Golden State Route that runs from Topeka to El Paso.
The first photo from 9:40pm shows the train echo between Mullinville and Bucklin. The track is located north of the highway from Bucklin to Cullison to Pratt. This is a wide view. The radar would be just off the image at upper left.
The next image (zoomed in) clearly establishes that it is a train on the UPRR. Between Greensburg and
The last image is at 10:14pm. Again, the echo is clearly centered north of US 54.
I have been watching trains since I was 5-years old and have been watching weather radar more or less daily since I was 19. I have never seen anything like this. I'm sure a temperature inversion diverted the Dodge City National Weather Service's radar beam toward the ground (meteorologists call it "super refraction") which is what made this image possible.
Update: From a Union Pacific employee posting at Trainorders.com, "Looking at the trains out there right now, there is an auto train, the APXLAR 11, that passed Wellsford at 10:08PM. That is about half way between Haviland and Cullison. Don't know what else it could be. The train is 75 empty auto racks."
And, in the interest of accuracy, there were some Trainorders users who reported seeing trains on weather radar before. If you are interested, go to: https://www.trainorders.com/discussion/read.php?1,4338439
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