Every cold shot this winter, even the Christmas cold to an extent, was a pretty quick in and out. The cold would become less and less on the models as we got closer to verification time, and the "cold" (what little there was) was almost immediately flushed out. Even the cold from this past weekend only lasted 24 hours or so. It seems the PNA is probably the most important piece of the puzzle. Not absolutely required, but without it, you're pretty close to having to thread the needle to get any kind of winter event. Just look at the snow maps over the next 10 days and it seems pretty obvious that pacific air is just ripping across the southern 2/3's of the country. Until the PNA approaches neutral (or hopefully goes positive), I think we're out of luck. A few weeks from now, even the positive PNA won't be enough for many.
TW