Beginning during the middle of January, waves of frigid air will be moving southward across North America from the North Pole.
Much of the nation experienced higher-than-average temperatures and lower heating bills so far during the cold weather season, with the exception of some bouts the past couple of weeks.
However, there are signs of a potential change on the way beginning the second half of January.
A phenomenon known as sudden stratospheric warming occurred in the arctic region during the first week of January. The stratosphere is located between 6 miles and 30 miles above the ground. Often when this occurs, it forces cold air to build in the lowest layer of the atmosphere then to drive southward.
The problem is the exact timing and location of the emergence of this cold air is uncertain. The effect is not immediate. Typically, the movement of cold air begins 10 to 14 days later. Discharges of the cold air can continue for weeks and shift from one part of the continent to another over time.
During week two of January, a flow of milder Pacific air will invade much of the nation.
Because of the time of year, some locations (the northern part of the Great Basin and northern New England) may hold on to the cold they have now due to long nights, light winds and weak sunshine. However, most locations will experience an upswing in temperature for at least a several-day period.
According to AccuWeather.com's Long Range Team, including Mark Paquette, "Overlaying this with other tools, we expect to see cold air spreading out from central Canada later this week into week three of January."
The cold will advance along in waves of progressively colder air with each wave driving farther south and east.
According to Long Range Weather Expert Paul Pastelok, "The indications are that the initial thrust of the cold will be directed over the West and northern Plains first, with subsequent thrusts of cold air pointed toward the Northeast and the Upper Midwest later in January and into February."
Expert Senior Meteorologist Brett Anderson stated, "Initially, the cold may seem to be run-of-the-mill or even delayed, but once the cold air engine starts, it may run for quite a while with progressively colder and colder waves of air."
According to Expert Senior Meteorologist Jack Boston, "As the waves of cold air spread to the south and east, some energy may be released in the form of a series of storms riding the cold air."
The storms may initially track from the Southwest to the Upper Midwest, then the western Gulf to the Great Lakes, the eastern Gulf to the Appalachians and perhaps finally northward along the Atlantic Seaboard.
Expert Senior Meteorologist Joe Lundberg added, "While a zone of high pressure off the southern Atlantic coast will offer some resistance to the cold initially in the East, most of the time in situations like this, cold air finishes the job and reaches the Atlantic Seaboard."
AccuWeather.com was expecting a stormy pattern to set up beginning the second half of January in the Eastern states and much lower temperatures this winter, when compared to last winter from the Mississippi Valley to the East in its Winter 2012-13 Forecast.
So while the atmosphere may seem to be settling into a pattern like last winter for some people, meteorologists at AccuWeather.com will be watching the evolution of the winter during mid-January with great interest.
Folks may want to check their supply of fuel for the second half of the winter sooner rather than later, in the event the waves of arctic air develop to their full potential. Folks in the northern Appalachians and parts of the East may not want to sell their snow blower and ditch their snow shovels just yet.
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