Cloud layers at specific altitudes require a special cloud/effects file to be loaded onto HTC's server. For this terrain, to the best of my knowledge, no such cloud/weather system has been built by our terrain team.
I may be incorrect in regards to the cloud layer, but for the KOTH's cloud layer at 6k, that was something DUX created, sent to skuzzy for building/loading onto the events server and is map specific.