According to Alex Sosnowski, Expert Senior Meteorologist for AccuWeather.com:
Moderate cold will first settle southward over the West during the latter part of this week into the weekend. Temperatures are likely to slowly moderate next week in the West.
Farther east, arctic air will spill into the northern Plains this weekend from central Canada and will progress southeastward in stages through next week.
Multiple storms could ride up from the Gulf of Mexico along the slowly advancing cold air over the Midwest and lower Mississippi Valley. It is possible that it will take a larger storm to finally drive the cold air to the East Coast during the middle of next week.
While it appears the cold waves will not rival the great arctic outbreaks of January 1994, December 1989 and January 1985 in terms of severity, it is possible that temperatures plunge 40 to 50 degrees over a 24- to 48-hour period as some locations pass from a warm air mass to the arctic air over the northern Plains.
For example, Fargo, N.D., is projected to have a high temperature well into the 30s on Thursday, Jan. 10, but before midnight Saturday, Jan. 12, temperatures may be well below zero.
Farther east over the Midwest, the cold air may advance and stop several times as storms roll up from the southwest.
The coldest weather around Chicago is likely during the second half of next week, when nighttime low temperatures may dip to near zero with a breeze stirring.
For the central Plains to the lower Ohio Valley and places on south, the arctic air may only be around for a few days before Pacific air mixes in from the west. However, additional waves of cold air are likely to follow later in the month.
In the Northeast, it will take longer for the cold air to take root. However, once it does arrive, it could be difficult to get rid of. There is some indication that steering-level winds, known as the jet stream, could dip southward over the region for an extended period aside from a few wobbles.
According to Chief Meteorologist Elliot Abrams, "Farther north and east (from the northern Plains to the central Great Lakes, New England and the mid-Atlantic), it is possible that the waves of arctic air may have more staying power, perhaps lasting a week or more instead of a few days at time."
In New York City, the current AccuWeather.com forecast calls for several days in a row with high temperatures in the 20s late next week into next weekend. Additional waves of cold air would follow later in the month, but the degree of warming in between the cold waves may be overdone.
Abrams added, "Long-range temperature forecasts have a strong trend to climatology, or normal/average, so that arctic outbreaks and their low-level cold air may be washed out by these overriding trends."
The core of the cold air and the center of high pressure does not appear to be aiming for the Deep South, but some arctic air will filter in.
According to Paul Pastelok, head of AccuWeather.com's long range team of meteorologists, "It is still uncertain as to whether or not it would get cold enough for a freeze in parts of central Florida at this time, but any such conditions are not likely until after Jan. 18 at the earliest."
In South Texas, there may only be a couple of nights where temperatures get low enough for borderline frost or freeze conditions and that is highly contingent on cloud cover, wind direction, etc.