I think you should support weather under ground also. They have a good API and it would not be hard. I have created an app that merged a list of weather stations from both NWS and WU (at the time most NWS stations could be gotten from weather under ground, but not all) to be selected from, and then retrieving the information can be done against both.
It has many more weather stations to choose from. What I found is that if you live close to the coast the NWS weather stations are not often right on the coast and the weather can be different just a few miles from coasts, and this is why we included Weather Underground.