Warmth is slated to precede a sharp cold outbreak that will occur in late January and into February. Above is my weekly forecast for January 6 to January 13th. I expect a zonal flow pattern to set up, with the jet stream displaced north and warm air overrunning much of the nation. This will certainly decimate any remaining snow pack, thus warming temperatures even further for areas around the previously snow-covered regions. The Madden-Julian Oscillation will be headed to Phases 5-6 during this timeframe, both of which are favorable for warmer than normal temperatures across much of the nation. As time goes on, the strength of the MJO signal in phases 5-6 is forecast to increase, only increasing the strength of warm air that will be present in the East US.
In Week 2, I expect low pressure to build across the West US and Rocky Mountains, and high pressure will then build on the East Coast in response to such an anomalous low pressure system. Colder than normal conditions will be displaced south, as the Arctic Oscillation goes negative and cold air presses south in preparation for the late January arctic blast. As the week progresses, I expect the low pressure system to move northeast into southern Canada, where it will stick around for awhile and bend the jet stream to provide cold air for much of the Plains. Eventually, it will bleed south and penetrate the entire nation later on in the month, when temperature anomalies as low as 10 degrees below normal could be found- and then some. The North American Oscillation should keep negative through Week 2, allowing for this bleeding cold air to at least try and push east. However, the still-unfavorable MJO and still-negative Pacific North American index (PNA) will inspire a battle to form between semi-warm air and frigid cold air. The frigid air will inevitably win out, but it could be delayed from hitting the East Coast thanks to these other teleconnections.