2:15 PM | **No changes from yesterday...extreme cold pattern setting up for the central and eastern US**

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Discussion

All indications continue to point to a bitter cold weather pattern setting up for the central and eastern US by the middle of next week and continuing into early February. This doesn’t mean that each and every day during this stretch will be bitter cold, but this period of at least a couple of weeks will average way below normal - rivaling the “polar vortex” cold of earlier this month in many areas - and widespread sub-zero readings will occur across the northern US perhaps even for extended periods of time. Chicago, for example, may actually have below zero temperatures for several days in a row during the last week of January.

The cause of this return to extreme cold will be a high amplitude weather pattern across North America with a deep upper level trough situated in the eastern US at the same time a strong upper level ridge extends up the west coast region of the US and Canada. In addition to these two upper level features, there is likely to be some “blocking” in the upper atmosphere across the northern latitudes (e.g., Greenland, polar region) that will help to sustain the bitter cold in the US for a longer period than the outbreak earlier this month. There will be numerous Arctic air outbreaks plunging into the central US from northern Canada and, from there, the dense cold air will spread eastward and southward to the southeast corner of the US. [The 00Z GFS Ensemble 500 mb height anomaly forecast map for next Tuesday night shows this developing upper level pattern; map courtesy Penn State eWALL].

As far as snow is concerned, there are a couple of systems that can give the Mid-Atlantic region a “weekend doubleheader” with a shot at snow showers late Friday night/early Saturday and again late Saturday night/early Sunday. It is also possible that some snow accompanies the transition to the bitter cold weather later Tuesday.

Get ready to hear the phrase "polar vortex" all over again.