I think the GFS wants to develop a bit of banding, especially against the transition zone to IP/ZR. That wouldn't be unusual. To the north it is better ratios getting the job done.
It was only a 1/2 inch on average lower than the 12z run. The overall coverage area was fairly consistent. It essentially held serve for this region. It increased a bit just NE.
Note the small differences in the vort max over TN along with the southern piece of energy. These subtle differences are going to make or break this event IMO.