HI Stephen,

Looking at the month to date temperature anomalies for Dec (Winter is Dec-Feb so we have a ways to go), temperatures in parts of the mid-atlantic are running between 0 and 1 degree below average. Not a huge negative anomaly but only slightly so.
https:/www.cpc.ncep.noaa.gov/products/tanal/temp_analyses.php

You are definitely right that the 6-10 and 8-14 day outlooks suggest that some cold air is headed that way which will likely increase the seasonal cold anomaly. But there is still a lot of winter left to go.

This is, though, a good example of the type of atmospheric phenomena that isn't entirely predictable when the seasonal outlooks are made, but whose influence is known to be strong on temperatures during the winter. This is one of the reasons that seasonal outlooks are in probabilities and those probabilities don't tend to exceed 60% chance.