Actually it goes by neither...The local on the 8's receive by viewers corresponds to the NWS Zone that covers your location.
Hers a link to show expamles of the various Forecast Zones in a given region.
National Weather Service Text Product Display..
You'll see as you scroll down the zones usually cover two or three counties. In areas where terrain is mountainous, weather conditions can vary greatly from lower to higher elevations. Those Forecast areas are smaller
That's not true for what I am getting. I am in Kentucky, with a NOAA station and radar 30 miles from me--that should be my weather station. However, the radar I saw was centered on WV.
In addition, the cities listed on the conditions segment are all in WV.
I'm sure this is because I am in the Charleston-Huntington DMA and get my locals from WV.