Thread: Arctic Blast via Polar Vortex to Chill 42 US States: -30° Wyoming...

Arctic Blast via Polar Vortex to Chill 42 US States

By Kristina Pydynowski, Senior Meteorologist

November 8, 2014; 9:06 PM ET



Video at the page link:

An overview of the weather across the North Central region is given in the above AccuWeather.com video.
As the polar vortex gets displaced to the south, the door will open for arctic air to plunge over the most of the United States as the new week progresses.
Only the Southwest, Hawaii, Alaska and South Florida will escape the grip of the upcoming arctic blast that the polar vortex can be blamed for.
"The polar vortex is a large pocket of very cold air, typically the coldest air in the Northern Hemisphere, which sits over the polar region," stated AccuWeather.com Senior Meteorologist Alex Sosnowski.
"Occasionally, this pocket of very cold air can get dislodged farther south than normal, leading to cold outbreaks in Canada and the U.S."



For this current outbreak, the harshest cold in relation to normal will encompass the northern Rockies and Plains. However, temperatures will also plummet throughout the Northwest and to the Gulf Coast and I-95 corridor.
The arctic blast will drop into the northern Rockies on Monday, accompanied by a snowstorm on its leading edge, then will spread across the Northwest and Plains through Wednesday.

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Later in the week is when the cold will reach the I-95 corridor, but it will not be of the same magnitude as earlier in the week.
Many communities across the northern Rockies and Plains will experience a 20- to 40-degree drop in high temperatures from one day to the next.
Tuesday and Wednesday will prove to be the coldest days of the week across the northern Rockies and northern High Plains, where highs will be held to the teens with subzero lows.

"The combination of cold air, wind and other conditions, including snow in part of the Midwest and northern Plains, will send AccuWeather RealFeel® temperatures plunging into the single digits and teens."
"Such cold will raise the risk of hypothermia and frostbite for those not properly dressed," Sosnowski continued.
Across the Northwest, South and I-95 corridor, the arrival of the cold air will create a December-like feel with a 10- to 20-degree change in high temperatures from the preceding day.
While the chill in the South and East will not be as extreme as what communities to the west are bracing for, Sosnowski is still urging people to winterize their vehicles and plumbing.



"Freezing temperatures are possible in parts of the South and East that have not yet had such temperatures this season."
Once the frigid air arrives, it will not be quick to depart.
Temperatures are expected to remain below freezing for nearly two weeks in the Upper Midwest, Minneapolis included.
The impending cold may set off lake-effect snow downwind of the Great Lakes later next week, when AccuWeather.com meteorologists are also monitoring the potential for a storm to bring snow to other parts of the Northeast.



Latest indications also point toward another winter storm crossing the nation next Thursday to the following Monday. With the cold air still in place, there could be a swath of snow stretching from the Northwest to the central Plains to the Northeast.
Enough cold air could even be in place for wintry weather around Portland, Oregon, and Seattle, Washington.
Continue to check back with AccuWeather.com for the latest details on the cold outbreak and any snowstorms.

http://www.accuweather.com/en/weathe...tates/37049255

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POLAR VORTEX WARNING: Latest winter weather models show UK faces MONTHS of heavy snow
uknw.co.uk

POLAR VORTEX WARNING: Latest winter weather models show UK faces MONTHS of heavy snow

November 11, 2014

A FREAK series of rare atmospheric events is set to plunge Britain into the worst winter of modern times with heavy snow paralysing the entire country within WEEKS.

Shocked forecasters warned tonight the latest high-tech weather models point to a CATASTROPHIC big freeze in late 2014 with THREE MONTHS of blizzards and Arctic gales.
They fear a lethal and unprecedented combination of low pressure, above-average rainfall and a freak Polar vortex will come together in a perfect storm of misery for Winter 2014.
Moist air from the Atlantic currently causing the mild, wet and windy weather threatens to collide with bitter Arctic winds.
It means a dramatic plunge in the current mild temperatures will turn torrential rain to blizzards capable of smothering the ENTIRE COUNTRY in feet-deep snowdrifts.
The big chill could arrive as early as this month although some models show the colder flow of air will be held at bay until the New Year.
However when it arrives, it threatens to rival the historic winter of 1947 which saw snow fall EVERY SINGLE DAY between January and March.
Crippling snow drifts of up to FIVE METRES ground swathes of the country to a standstill while the armed services were drafted in to drop emergency air supplies to stranded communities.
In a terrifying similarity to this year, the killer whiteout of 1947 started with suspiciously mild conditions persisting into early winter.
Worried experts have warned Britons not to be lulled into a false sense of security by the current benign conditions.The very latest weather models show a unique set of circumstances coming together to create an extreme whiteout driven by violent snowstorms.

James Madden, forecaster for Exacta Weather, said a strongly negative Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) this winter are main driving factors.
Both phenomenon are governed by atmospheric sea pressure and when in a negative phase they allow cold air to flow in from the East – the so called blocking effect.
Mr Madden said due to recent warming in the Earth’s stratosphere, both the NAO and AO are “excessively” low pointing towards a severe freeze.
A separate measure derived from air flow patterns in the upper atmosphere called the October Pattern Index (OPI ) also points towards a negative Arctic Oscillation.
The resulting weak jet stream, which usually holds the cold at bay over the North Pole, will give way to a blast of freezing air which will sweep across the UK.The OPI was devised by scientists Riccardo Valente and Professor Judah Cohen with this year’s readings dangerously similar to those taken during the catastrophic winter of 2009/10 – the coldest in 31 years.
Experts say a crippling big freeze could be as close as the middle of this month and has the potential to last until spring.
Mr Madden said: “The important pieces are now becoming grouped together to form blocking episodes throughout the second half of November and the upcoming winter period.
“This is reflected upon with the obliterated Polar Vortex and the downward trend of the ‘excessively abnormal’ Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) values, due to recent stratospheric warming and higher than normal pressure across the Arctic region.
“When the AO is in its negative phase, it allows for an easier intrusion of cold Arctic air to lower latitudes such as the UK.
“When the closely related NAO is also in a negative phase, it allows for cold easterly winds and much cold winters to develop.”

http://uknw.co.uk/polar-vortex-warni...of-heavy-snow/