I've used WeatherBug for a long time, even with my BlackBerries. Not only are there no ads (very annoying to have those), it has weather stations close to where I live. My home is in hilly terrain inland and most weather services have stations in the more populated areas along the ocean's coast. Around here, there is a MAJOR difference in the weather from one area to another. WeatherBug has been very accurate. Also, it makes sure alerts are pushed as they occur.
I now have the "elite" version on my X and it maintains it's outstanding track record for me. Excellent app.