-NAO -NAO -NAO -NAO -NAO
Yes, having a +PNA is wonderful. We need it. It's imperative. Combine that with a -EPO and we can get (and stay) cold as we just seen. -AO? You bet, we need it. -PNA/-AO combination is paramount. But we have seen over and over and over and over again the importance of a -NAO. If we have to rely SOLELY on TIMING a HP moving in tandem with a wave all the way across the nation to score, well, the results speak for themselves. We can score with the +PNA/-AO combo, and we have (DEC 8) but in order to get more of the SE involved, we MUST have a -NAO to slow the flow so we don't HAVE to rely solely on timing. Even if it's just for a few days (and most of the time since 2009, we've only had it for a few days at a time.) we absolutely must have it to score widespread across this forum.
If we have a +PNA/-AO combo, we have about a 10% chance of a widespread, legit winter storm. Give us a -NAO and I'd say that increases the chance to closer to 50%.