Arctic air is on the move and December will be significantly colder when compared to November for much of the eastern two-thirds of the nation as a result.
The movement of cold air will be much more aggressive during December than what we have seen during November for the Plains, Midwest and part of the Northeast.
According to Long-Range Weather Expert Paul Pastelok, "The cold waves, although transient, will likely produce either near-normal temperatures or even below-normal temperatures for much of the Plains and the Northeast."
December is typically colder than November, on average. That's a "no-brainer."
However, during this December, some places may average more than 20 degrees colder than November.
"For some people that will be quite a shock," Pastelok said.
In Chicago, for example, the normal average temperature for November is about 41 degrees. During December, the normal average temperature is around 28 degrees.
So, even if December ends up being near normal for your location, it will be substantially colder than the blissful November. November brought temperatures of 2 to 6 degrees above normal over much of the central and eastern United States.
Chicago could average several degrees below normal during this December.
Despite the expected much lower temperatures, it does not appear there will be long-lasting frigid weather for most places this month and the core of the cold will sputter upon nearing the Atlantic Coast and may have trouble arriving at all over the Southeast.
The real frigid days over the northern Plains and the Upper Midwest will be canceled out by a few days of slightly above-average temperatures. Hence the in-and-out effect. But, that means there will be some days with highs in the single digits and teens in the region and perhaps no days with highs in the 50s and 60s.
Waves of arctic air will sweep down from the Canada Prairies dive into the Plains then sweep northeastward before lifting out.
The worst and most of the cold waves will tend to avoid the southeastern U.S.
The roots of one cold wave are already being established in the West now. That cold air will ooze eastward over the Plains this weekend and then into the Northeast early next week.
A much more substantial blast of cold air will follow during the second half of next week and will bring the lowest temperatures of the season so far over much of the Plains and the Upper Midwest. However, that too will lift out after several days.
One argument toward generally colder weather in the central and to some extent in the eastern U.S. is the retreat of frigid air from Alaska.
Depending on where the leading edge of the cold air pauses or runs out of gas will determine the storm track during this period. Odds favor this track being well inland of the coast.
There is the potential for multiple storms to track from the South Central states to either the Great Lakes or the Northeast. The exact track of each storm will have great impact on which areas get snow, which areas get rain and which areas get little or no precipitation.
This story was originally published on Tuesday, Nov. 30, 2011 at 1:00 p.m. EST.
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