Taking the 18Z GFS verbatim (looking at hour 150, 0Z 11/16), moisture actually isn't that much of an issue, surprisingly, for the northern end of the potential setup. Upper 50s well into Iowa, which is plenty for a cool season setup. Vertical depth is plenty adequate, too. In fact, on some of the forecast soundings the profile is quite saturated up to above 500mb, making for p***-poor lapse rates which is what kills the instability, not lack of moisture.
The only other thing is the E-W breadth of this moist axis is somewhat narrow, with low 50s out in Illinois and even into northern Mississippi/Arkansas. This would limit the amount of real estate you have for storms to work with. I think part of the problem is the trough off the Atlantic seaboard amplifies at the same time the trough coming into the west does, creating kind of a pinched off ridge with a narrow wavelength between them. If that ridge were a little wider and able to push off the Atlantic coast a little more, you would get southerly winds across the whole Gulf sooner. As it is they appear to remain easterly across all but the western Gulf until early Saturday morning 11/15 (the day of the potential event).
Certainly interesting, though and the first real synoptically-evident setup we've had to track for a while.