A blast of Arctic air advanced over much of the U.S. on Thursday, triggering dramatic temperature drops as a storm the National Weather Service called a “once in a generation” blizzard was brewing in the northern part of the country.
States including Wyoming, Colorado and Montana have already recorded significant temperature plunges and more than a dozen others had readings below zero Thursday morning.
More than half of U.S. states were forecast to see some areas with minimum wind chill temperatures in the negative double digits in coming days, and the coldest regions were bracing for wind chills below minus 50 degrees, according to the National Weather Service. There will be “dangerously cold conditions across most of the country this week,” the weather service said.
High winds combined with even moderate amounts of snow could cause blizzard conditions in parts of the Midwest, Great Lakes and Northeast.
Forecasters warn the weather could snarl busy holiday travel and knock out power.
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Winter storm snowfall totals accumulate
Minnesota appeared to accumulate the highest reported snowfall amounts Thursday morning, according to the National Weather Service. An eastern portion of the state’s population is among over 60 million in the U.S. under a winter storm warning.
The unincorporated area of Tofte, Minnesota, saw 12 inches of snow by 9 a.m. EST, while 11.7 inches fell in Lutsen, Minnesota, 9 miles northeast of Tofte. Meanwhile, Rollinsville and Nederland, Colorado, saw snowfall totals Thursday morning of 9.8 and 9.5 inches, respectively.
Flights canceled, delayed amid winter storm
Chaos has already ensued for holiday travelers dealing with flight cancellations and delays Thursday. The winter storm slamming the central and eastern U.S. has led to at least 1,400 canceled flights as of 9:30 a.m. ET, according to FlightAware. Some airlines preparing for the disruptions have begun issuing travel waivers in the Midwest, Northeast and parts of the South.
Flight canceled? Here’s what you need to know.
What is a bomb cyclone?
Forecasters expect the winter storm to quickly strengthen across the country’s center – a process and phenomenon called bombogenesis, or a bomb cyclone. That’s when the atmospheric pressure of a mid-latitude cyclone swiftly drops, according to the National Oceanic and Atmospheric Administration.
A bomb cyclone happens when a storm’s barometric pressure dips by at least 24 millibars – a way of measuring pressure – in 24 hours, according to AccuWeather. The lower the pressure, the more powerful the storm.
What is wind chill?
Some areas faced wind chill temperatures well below zero Thursday – such as Chicago, with an expected wind chill of -40 F by Friday night – as the winter storm freezes much of the upper portion of the U.S.
Meteorologists define wind chill as how cold it feels while outdoors, and it’s based on the rate of heat loss from exposed skin caused by the wind-and-cold combination, according to the National Weather Service. Increased wind draws heat from the body, which then lowers the temperature of the skin and internal body.
“Frostbite may develop on exposed skin in as few as 10-20 mins, and hypothermia can quickly develop if you’re not dressed for the cold,” weather service experts in Chicago warned Thursday.
What is lake-effect snow?
The brutally cold conditions are forecast to trigger lake-effect snow in some places like New York’s Buffalo-Niagara metropolitan area, which is under a blizzard warning.
Lake-effect snow develops from cloud bands that form when cold, dry arctic air passes over a large, relatively mild lake. The phenomenon can last from a few minutes to several days.
‘The bottom keeps falling out’: Temps plummet across the US
The freezing air has hit some areas of the country with a vengeance, at times transforming temperatures in a matter of minutes.
The National Weather Service reported rapidly falling temperatures in Wyoming Wednesday night. The weather service’s Cheyenne, Wyoming, office reported a 56-degree temperature drop in six hours, a record.
The weather service in Boulder, Colorado, reported a 37-degree drop, from 42 F to 5 F, in the span of an hour in Denver Wednesday night.
In Dillon, Montana, a weather service office reported a 26-degree drop in three minutes.
The cold front is forecast to dive into the South as it moves farther east. Forecasters warned of potential flash freezing in areas where moderate rain may fall, and more than 130 million people faced dangerous wind chills late Wednesday.
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How are regions being impacted by the winter storm?
- Midwest: Some areas in the Midwest and the Great Lakes region could see blizzard conditions until the end of the week, according to AccuWeather. Light to moderate snowfall and strong winds are forecast for the region with heavier snow predicted to exceed a foot over the Great Lakes through Friday. Oklahoma Gov. Kevin Stitt declared a state of emergency on Wednesday for all 77 counties.
- Northeast: The storm system is expected to hit the Northeast with a number of hazardous and disruptive weather conditions in the days leading up to Christmas, according to AccuWeather. Mostly rain and strong winds are expected ahead of the storm Thursday and Friday. But some portions of the region may experience snow as the blizzard moves east from the Midwest. The rain and snow will put the region at risk of flash freezing, according to AccuWeather.
- South: The storm will hit the South with wintry conditions and a deep freeze according to AccuWeather. As temperatures drop, more than 4.4 million people were under a weather service-issued hard-freeze warning in parts of Louisiana, Alabama and Mississippi on Wednesday. Wind chills with subzero temperatures may move into Texas and parts of the Deep South through the week’s end, the weather service said.
Contributing: Zach Wichter, USA TODAY
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