The Madden-Julian Oscillation - "The largest element of the intraseasonal (30- to 90-day) variability in the tropical atmosphere. The Madden–Julian oscillation is a traveling pattern that propagates eastward at approximately 4 to 8 m/s (14 to 29 km/h, 9 to 18 mph), through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall" - Wikipedia
With MJO going back into Phase 4 and neutral AO, feel like core of the cold will be delayed until late January or possibly February. In the meantime still colder than average. We will see the stormy pattern continue across the Midwest. Hopefully we can get a storm or two in Wisconsin.