Figured I'd drop by to comment on this one.
The depiction from the Euro has pretty consistently been rather alarming, with the most recent 12z run perhaps being the most troubling of the bunch across a very large expanse of real estate Monday evening into Tuesday afternoon (basically from E TX and SE OK all the way into GA and perhaps even the Carolinas). It is really important to remember that with these events later in the year, destabilization will be driven as much, if not more, by advective processes versus diurnal diabatic heating (i.e. the sun). This is especially true given the powerful low level jet being suggested in some model depictions. In other words, destabilization after dark ala 11/29-30/2016 amongst a host of others.
Such a broad based trough with strong deep layer shear oriented favourably to the initiating boundaries will clearly favour a semi-discrete/discrete storm mode for a long period of time. The magnitude of deep and low level shear would clearly favour long-lived, fast moving supercells with significant tornadoes assuming adequate destabilization can take place.
There is still a fair amount of disparity here amongst the model suites, but the consistency of the Euro and its ensemble members lead to me to believe that there could be some serious problems here. This is one to really watch.
