The NAO or North Atlantic Oscillation is simply a "blocking" pattern that allows for cold air to slow down and allows LOW pressure to form off the coast and has time to explode into snowstorms.
It's basically the traffic cop of weather. Slow the pattern down and the odds of a juiced up system getting into the Eastern Part of the U.S. starts to increase. Negative NAO = More storm chances east of the Mississippi River.
Some of our analog years for the winter and Wisconsin:
A wide range in totals in a few of the selected analog years, but we are going to weight the 2006-07 year a little bit more for a few reasons. First, it is an el nino following a la nina winter / neutral winter.
Second, the PDO is negative right now and based off trends expected in October we expect this to become closer to a neutral PDO in a el nino winter just like 2006-07.
However, if it remains a negative PDO an analog that might get more weight is 1951-52 when Milwaukee received over 90"! The QBO was weakly positive (forecasting it to be weakly positive in winter).