I just had a look at the 00z run of the GFS and NAM, all I can say is WOW! The models are now coming into agreement the ECMWF has shown a negatively tilted trough for some time, but as of the 4-12 0z run the NAM / GFS are coming into agreement. GFS / NAM now show a negatively tilted 500mb trough with a ski jump! The GFS has quite a bit less instability compared to the NAM and the moisture return is a tad on the iffy side. But with upper level dynamics of this magnitude this could turn out to be quite the event it’s worth watching to see if the models fail anyway.   It’s a day or so too early for me to get really excited I will try and post some updates throughout the next few days. I have attached some model forecast charts from twisterdata.com   Here are some links to Jeff Haby's page that explain some of the topics like negatively tilted trough and the ski jump (divergence / diffluence) aloft WHAT IS A "NEGATIVELY TILTED TROUGH"? THE SIMPLIFIED OMEGA EQUATION Tyler.