Are there any other reports of this? I am always dubious of articles that start with speculation before they bother to inform you about what “it” is. The description by the meteorologists should have been the lead.
Was the plume dense enough to obscure the detection of planes passing through? If so, then it was probably a test of radar blocking technology.
Darn good question: If it was, then it was pretty irresponsible - especially since it lasted so long. Underneath that radar signature is a commercial airport. I suppose if I were a real reporter (and did things like 'investigate' stories... I know: that's a reach), then I would be quizzing the ATC guys at HSV.