As seen above, the 11-15 day average for 850mb temperature anomalies is very cold- as low as 14 degrees below normal. This actually puts the 850mb temperatures cold enough to produce snow- an occurrence being shown by the same 12z GFS.
As is to be expected, the long range verifies a very small part of the time, so one would usually take this with a grain of salt. However, looking at past trends of the last few runs of the GFS focused on 11-15 day 850mb temp anomalies, the model has been steadily trending colder with each run. What I would take away from this is that an enhanced appearance of cold weather is likely in the next couple of weeks, but the intensity is unknown.
Considering there is a strong disturbance anomaly over south central Canada and central Canada, there should be at least one storm system that sweeps cold air east and into the Midwest and Mississippi Valley. The west-to-east motion of systems in the North Hemisphere means that this cold air will eventually move east into the eastern US, but the intensity of that cold air is in question.