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Weather: The big chill?

The 8-14 day outlook from the Climate Prediction Center calls for a high chance of colder-than-average temperatures across much of the western and central U.S.

The 8-14 day outlook from the Climate Prediction Center calls for a high chance of colder-than-average temperatures across much of the western and central U.S.

Forecasters warn of possible ‘Arctic outbreak’ in mid-January

By Summit Voice

FRISCO — A sudden stratospheric warming in the Arctic region may push extremely cold Arctic air into parts of the mid-latitudes during the next few weeks, according to forecasters with AccuWeather.com, who say the Arctic outbreak could start in the Pacific Northwest and then move into the northern Rockies and the central U.S.

Sudden stratospheric warming is considered by some meteorologists to be among the most dramatic atmospheric events, occuring when the westerly winds of the polar vortex slow down, or sometimes even stop and reverse direction. When the stratosphere, between 6 and 30 miles high, warms, it forces cold air to to build in the lower levels of the atmosphere and eventually surge southward.

The timing and location of the emergence of the polar outbreaks are uncertain, but generally, the cold air starts to march southward about 10 to 14 days after the warming event in the stratosphere.

So far this winter, much of the nation has been experiencing higher-than-average temperatures, but that could change by mid-January.

“Overlaying this with other tools, we expect to see cold air spreading out from central Canada later next week into week three of January. 

It is possible the cold push will arrive in one big blast. However, it is more likely the cold will advance along in waves of progressively colder air with each wave driving farther south and east,” said AccuWeather.com’s Mark Paquette.

“The early indications are that the initial thrust of the brutal cold will be directed over the Northwest, northern Rockies or northern Plains first, with subsequent waves reaching farther east,” said AccuWeather’s long range weather expert Paul Pastelok.

“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,” said meteorologist Brett Anderson. “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,” he said.

“

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.

“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,” said meteorologist Joe Lundberg.

AccuWeather.com expects 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.

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