I’d recommend weawow, it’s what I normally use. You can choose a source for your weather data, rather than just being stuck with whatever the developer chooses. Weather underground is okay. It used to be a lot better before IBM bought them out, but the UI isn’t too terrible. Carrot is also somewhat decent from what I remember.

If you need a rock solid radar app, radarscope is phenomenal. If you’re into viewing predictive model data, flowx is probably my most used weather app during non-tornado season.