I was able to find seats departing Philadelphia PHL on Friday, December 7, returning from Nashville BNA on Monday, December 10.
Other dates are available for travel on Mondays, Wednesdays, Fridays, and Saturdays in October/November, and Mondays/Fridays only from December through mid-February, excluding peak holiday travel.
Similar fares are available on Frontier, but you'll pay more for baggage. Southwest includes two free checked bags and has no change fees.
Need a room in Nashville? Here's what's available for the above dates on Hotelwatchdog.