That's an interesting little feature isn't it... Actually, if I didn't know any better I'd suggest we are looking at at supercell. Notice when looking at visible imagery that the area on it's backside suddenly clears out, as a band extends cyclonically in its right exit region as the system moves N. This is classic. We see this in the Plains states during severe weather outbreaks. Basically, dry air/subsidence into the back side is clearing it out as the ingest on the front side draws in warm unstable air. This way, the warm ingest is not being impeded by the relatively stable air on the backside and the storm is allowed to perpetuate - i.e., supercell. Doesn't necessarily mean a tornado is on the ground or anything like that, but, it is wise to have a tornado watch in effect for the areas N and NE along the coastal plain of SC. Fascinating.