It's amazing how the NAM continues to trend toward the consistent UKMET/ECMWF. This goes to show how poor the NAM is beyond 36 hours. I rarely the NAM for anything beyond 36 hours.... or just use it's thermodynamic forecasts and mentally shift it towards the UKMET surface features..
In fairness - with systems moving as quickly as they are this time of year combined with a zonal flow pattern - you have to think of long-range ETA as nothing more than a high resolution GFS - because all that you are seeing after 36 hours is what came in on the western boundary condition, which comes from the GFS forecast. NAM is only adding some better physics and terrain, not a whole lot more. Once the system is within the observing network - the NAM can finally start to get a better solution, and with this system this only became true this morning with just the nose of the upper jet sampled at VBG.
[mets only note]Also, in fairness the ideas suggested about the importance of low-level buoyancy were actually brought up by several I believe long before Jon Davies. I think of the work by McCaul and Weisman 1996 in particular. I also love to look at the 0-3 km CAPE for signs of potential tornadic activity - but I don't know how much I would trust a model forecast of it ~33 hours out.[/mets only note]