That's definitely part of it. I think you eventually don't see that difference once SSTs to the south warm up a bit. I also noticed (especially yesterday) modeled showed the best warmth 925-850 over that area so it makes sense why it was so warm there yesterday. Today that is more widespread.
I doubt it. We had a good cold source for many of those events. Our biggest problem is that we have no good highs that anchor north of Maine or over in Ontario. If we had that 07-08 look again, I wouldn't expect much difference at all.