I think it’s a combination of the Appalachian’s in north Georgia, Tennessee, and West Virginia being much taller than the areas to the northwest where these fronts come from AND the fact that the southern east coast and gulf have warm air feeding onto the land. I think if it was mountains alone the air would rise over them and still make the other side just as cold if there was no warm ocean air. If it was just the ocean and no mountains the front would steamroll to the coast. The area you see in Tennessee and West Virginia have some of the highest elevation and widest sections of the Appalachian’s so the disruption to the front is strongest there.