From the 70s into the 90s, many TV stations maintained their own weather radar facilities. Such was the case for Channel 6. This, or was, theirs, at the transmitter site. All these facilities had range limitations over curved earth. Today TV stations use other services like (or perhaps the same as) those employed by weather.com — which I presume is the NOAA or providers of NOAA data. Don't know, though. If anybody does, add it to the comments below. Here is Wikipedia's encyclopedic entry on weather radar. And here is the current National Weather Service doppler radar loop for the whole country (animated with Java). Continue.