Sorry not NG but big steam for Colorado area.
I saw a post on another site and they indicate a few double headers this week from Denver to Cheyenne with Challenger No. 3985 and No. 844.
Not sure this is accurate as the Denver Post web page says just 844?
They also listed this:
There will be four trips between Cheyenne and Denver:
-- Thursday, the train will travel from Cheyenne to Denver, passing through Greeley about 11:30 a.m.
-- On Saturday, there will be two trips; the trains will pass through Greeley at 8:45 a.m. and later at 6:30 p.m.
-- At 2 p.m. Sunday, the train will pass through Greeley one last time, making the return trip from Denver to Cheyenne.