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.
Put the NAO and AO in sync and a nice dose ofmoisture and you lean toward an above average winter in East and in the Rocky Mountain Region. Could it be like 2009-2010 or 2002-2003 ? Maybe but we are just too early in the game to look at that yet.
The positive phase shows warmer water building up in the Gulf of Alaska and along the Western US. This would favor a +PNA pattern with riding along the Western US and a trough downstream into the Eastern US. A negative phase would favor the opposite with a western US trough.
Some analog years for Pittsburgh, PA for the upcoming winter with NAO values for the month followed by snowfall for that month.
The NAO is a very important factor, but obviously there is exceptions such as 2003. When 25.3" was recorded in a month with an overall positive signal of the NAO.
Given the expected neutral- Weak El Nino signals combined with a negative NAO we expect slightly above avergae snowfall in the Pittsburgh area.
Update Nov 28th
BELOW AVERAGE TEMPS
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