I started having the same problem last night when it would only say Weather Add City. I could add a city and as long as I unchecked use current lcoationl it worked fine. It went back to Weather Add City if I checked the use current location. However, every once in a while, it would pop up the weather fine before going back to WAC. This afternoon, it appears somewhat better and seemed to track my location as I drove from New Jersey back to PA. I'm guessing it is something on their side because I didn't update any apps or change anything since last night.
Rgds/Mark M.