Cold wave by the last part of January or will it be just a return to seasonal?

I don't believe the hints at severe cold for New Jersey, New York Metro around Jan. 20th.  The strong Pacific jet stream wind, a Southeast ridge and a PNA that is too far West means the cold air will struggle to get here.

Canada will experience extreme cold, but I doubt that it gets past New England.  We will see.

It is looking like the cold front will get hung up over the Eastern US, with  lots of stormy weather and a variety of frozen precip. and rain.  Some snow is possible along with ice.  All after this coming mild week.