As Ink said, BNA is very navigable. It is probably a five minute walk from the most outlying WN gates, but the majority of them are about a 90 second walk of each other. I do agree that I'd probably grab the first seat(s) available towards the front of the plane enroute to BNAjust to save some time deplaning, but generally speaking 30 minutes at BNA is plenty (and the weather appears that it shouldn't be an issue at this time).