Lastly, we are increasing the charge to check a third bag and heavy bags onboard our aircraft. Dont worry, you can still check two pieces of luggage for free on Southwest Airlines-- that has not changed--but beginning June 17, Southwest will increase the amount currently charged to check overweight bags weighing 51 to 70 pounds and excess luggage from $25 per bag to $50 per bag. All other checked baggage policies and charges remain the same.
They are also going to charge a $25 administrative fee each way for unaccompanied minors.
My friend was over and had to do some last minute repacking to get under the limit in both of her cases. 
