This post will show the GFDL model's long range forecast for the December-January-February 2013-2014 period. Additional models will be shown on here in the future.
The image above shows predicted 200 millibar contour lines and anomalies. We're going to focus on the contour lines for right now. We start in East Asia. Looking closely at the image, we see tightened contour lines in the area around Japan. Considering there is a 6-10 day gap between storm systems in the East Asian area and storm systems in the East US, a tightening of contour lines could suggest an increased number of storm systems. This, in turn, may suggest a stormy East US this winter. We see a large ridging pattern across the Alaska/western Canada. This ridging could then provoke a colder than normal pattern to evolve across the Midwest and East US, as cold air flows southeast along the ridge. If the ridge extends far enough into Alaska, a cross-polar flow situation could set up, which would transport Siberian air to the States. A cross-polar flow is one of the situations that brings the coldest air possible to the US- another situation would be the cold air displaced to the surface as a result of a stratospheric warming.
More of these posts will come out as we dive into fall and closer to winter.