The Difference Between Raw Radar Data & QC Radar Data
The picture above is currently on 'QC Reflectivity'(Quality Controlled Reflectivity). This is meant to filter out a lot of the clutter you see when a radar site is in clear air mode. Sometimes though, the algorithm can get it wrong and QC out something that is actually a storm or precipitation of any type. As you can see in the picture above, there is obviously some thunderstorm activity going on in that area, but nothing is showing up DBZ wise. This would be one of those instances where the algorithm got it wrong, to fix this just switch to the 'Raw Reflectivity'.
As you can see from the image above, the highlighted area is now showing the thunderstorm activity. However there is now 'Clutter' showing up near a radar site to the southwest. In most cases the algorithm will normally catch this error pretty quickly and correct it within a couple of updates.