I forget the EXACT terminology -- tropo; ducting; something like that -- but there's a seasonal atmospheric phenomenon that begins wreaking havoc (or pleasure if you're TRYING to hear the offending signal) on FM signals from now until early Fall. And...it is typically worse in the morning hours. Here in Morganton(NC) this time of year, I begin getting interference favoring central and coastal NC signals.
So, if you've just begun to notice WGBT's interference, it may not be their fault but the atmosphere's.
Eric