Polar vortex: Most of the country should be preparing for a bitter cold snap

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A “flash freeze” could accompany this storm, as the temperature drops as quickly as one degree per hour, quickly freezing any rain or melted snow left on the ground.

A “flash stop” occurs when rapidly falling temperatures “quickly turn wet or muddy roads to ice,” noted the Des Moines National Weather Service, warning it will likely cause significant travel problems in Hawkeye State on Thursday.

The arctic cold will not spare the rest of the country either. Monday morning, 235 million Americans, or about 86% of the country, will face freezing temperatures. This includes every state in the Lower 48.

Blizzard sets the stage for extreme cold

Strong winds, drifting snow and rapidly declining temperatures are expected from Nebraska to Michigan through Friday.

Snowstorm warnings are in effect in Central and Northern Iowa through Friday morning, while winter storm warnings and advisories extend further east to Chicago and Grand Rapids.

The snow storm criteria do not necessarily require snow to fall from the sky.

As with this storm, only moderate accumulations are forecast, ranging from 2-5 inches in Des Moines and up to 8 inches in Green Bay. Higher totals can be expected downwind from Lake Michigan in the favored Lake Effect areas, where up to 12 inches of snow is possible.

Ahead of the system, a wintery mix of rain and snow is forecast as temperatures rise briefly before dropping dramatically behind the cold front.

Winds are expected to blow more than 45 miles per hour, gush snow, and reduce visibility below a quarter of a mile in parts of Iowa. When the mercury drops and the snow starts to drift over roads, conditions will worsen in an instant.

Waterloo, Mason City and Fort Dodge will all experience “extreme” travel impacts from this powerful storm, according to the NWS Hazard Matrix.

Even though there are blizzard warnings, high snow totals will not be the biggest threat from this storm. The real showstopper is the cold air that settles early next week.

A flash froze to hit the Midwest

The coldest air will dive south through the upper midwest and the Great Lakes on Saturday. In places in Central Wisconsin, temperatures can drop to -25F on a Sunday morning, with high temperatures struggling to get to zero. Nighttime lows can be cold enough for your car’s antifreeze to solidify.

“We get two to three of these cold snapshots every year,” said meteorologist Marcia Cronce of the National Weather Service Office. “We’re going into the coldest air of the season, it will feel choppy.”

“As temperatures drop some 25-30 degrees below the seasonal average, parts of the Upper Midwest will approach the thresholds needed to cancel classes or, in the case of 2021, virtualize,” said CNN Meteorologist Pedram Javaheri.

St. Paul school districts are scrapping classes if the 6:00 AM forecast for the next day is -25F or if the wind chill will drop to -35F.

The polar vortex is coming

This frigid cold compliments the polar vortex, a large area of ​​low pressure near the poles. During the winter months, it breaks down and sends cold air that has been bottled up. It can be responsible for extremely cold temperatures and massive amounts of cold air.
The polar vortex has been weakened even more this year by the sudden stratospheric warming that occurs about six times a decade.

This will cause the polar vortex to weaken even further, creating bitterly cold conditions.

The cold trend will continue for the next 10 days.

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