The first panel shows a strung out shortwave in Texas interacting with energy dropping down from Canada at 500mb. There is no defined low at the surface either, yet panel two shows a wave of precipitation riding along the frontal boundary draped over the upper Ohio Valley and northern mid-Atlantic. The black line is freezing at the height aloft at 850mb. Everything north is below 32 degrees Fahrenheit. This a textbook “overrunning” event.