What is this on weather radar?

Noticed this on weather radar near Nashville. Of course the weather is moving East to West, but that’s not what I’m asking about. You can see this storm moving west and what I am used to seeing as a gust front or a storm burst. But it is at the top of the storm and follows behind it.

I am not a meteorologist and do not play one on TV, but I did stay at a Holiday Inn Express last night. My best guess is this is the normal verga that would be seen on radar as the sun sets and the air cools. The radar just makes it appear this way?

Can someone explain what is actually happening?