The map you just posted isn’t actually a “traditionally” neg PNA, but a transient gradient pattern where the index “computes” negative for a few days. More like a bootleg -PNA. However, I would feel better if we didn’t have troughing in the pac NW. We’d want ridging there to maintain the cold supply as the storm approaches here (even as a cut off low or energy undercutting the +pna ridge). I do like the atlantic side, we have a PV pressing down south towards us with confluence.
The biggest failure risk is that the western trough gets stronger, the TPV retreats north or NW, and the eastern ridge pumps, and the storm cuts. So far we haven’t been trending in that direction, though.
The other end of the spectrum is where the PNA is so positive (with -EPO) that it suppresses the storm south. Right now that is the most unlikely scenario for that window.
In short, with -EPO and a strong TPV in SE canada, we’d root for a neutral PNA if not slightly positive. In this case, too much -PNA, cutter. Too much +PNA, suppression. But generally, we get our best snows snowstorms when the PNA is positive.
btw this is why we like El Ninos. STJ undercuts the +PNA, which delivers the cold while we get gulf moisture from a STJ wave. Way simpler than trying to thread the needle during a Nina.