I think it cycled after hitting Samburg, and then the Mayfield tornado started SW of Cayce, likely took out that town, then continued for over 150 miles.
Major tornado damage in Samburg TN near the end of the path of the first long-tracked, violent tornado from the main supercell (which was indeed a tri-state tornado).
So that 16z HRRR is probably nudging towards territory that would warrant pink in the convective outlook. Multiple pre-frontal supercells in highly volatile shear/sufficient low-level buoyancy environment.
Have some 2/28/2017 vibes from that 12z HRRR run. We are dealing with some pretty incredible moisture for December (or any cold season month, really) and it should get pretty far north given the lack of morning convection.
Period around next weekend has potential (that will probably be squandered). Certainly cold air available and a substantial baroclinic zone if we do indeed get a wave ejecting around that time.