Primary radar shadow (in red) & Cedar Mountain shadow (in orange)
The GSP radar site has two coverage gaps which can be misleading,
especially with weather events coming from the west of WNC.
Ironically, the extent of the radar shadow gap can best be seen when it's raining reasonably heavily, as seen in this example.
The primary shadow is caused by the mountain that is on the SC-NC border along which I-26 runs.
A secondary shadow occurs because of Cedar Mountain to the west of the primary shadow and extends to Sevierville, TN.
FAA and NOAA/NWS coverage maps are available, but are difficult to keep track of. "Extensive updates" of February, 2018 have been unable to plug the gaps, even assuming mixed mode (H/V) upgrades.
Path obstruction diagrams
The WDS-88D radar does a fantastic job through such terrain, but images with small targets (e.g. tornado) should be treated with care in these areas.