The frost has hit North America

A pedestrian navigates a snow-covered crosswalk in Chicago, where high winds and sub-zero temperatures are forecast for Friday, pushing wind chills to minus 40C.  (Reuters photo)

A pedestrian navigates a snow-covered crosswalk in Chicago, where high winds and sub-zero temperatures are forecast for Friday, pushing wind chills to minus 40C. (Reuters photo)

A deep freeze swept through most of the United States early Friday, while a massive winter storm brewing in the Midwest put two-thirds of the country under extreme weather warnings and disrupted Christmas travel plans for millions.

Heading into the bank holiday weekend, the looming storm was forecast to develop into a “bomb cyclone,” unleashing heavy, blinding snow from the northern plains and Great Lakes region to the upper Mississippi Valley and western upstate New York and would expand north into Canada.

The numbing cold, enhanced by high winds, was expected to extend to the US-Mexico border to the south.

Freeze warnings were issued in the Gulf Coast states of Texas, Louisiana, Alabama and Florida, while significant icing was possible from a separate Arctic blast that hit the Pacific Northwest.

As of late Thursday, most of the lower 48 states, from Washington state to Florida, were under wind chill warnings, blizzard warnings, or other winter weather warnings, affecting more than 200 million people, about 60% of the population, according to the National Weather Service ( NWS) reported.

The NWS map of existing or upcoming winter hazards, stretching from border to border and coast to coast, “displays one of the most comprehensive winter weather warnings and advisories ever,” the agency said.

The bomb cyclone could unleash snowfalls of 1/2 inch per hour, driven by gale force winds and reducing visibility to near zero, the weather service said.

In combination with the Arctic cold, wind chill factors of up to minus 40 degrees Celsius have been forecast in the High Plains, northern Rocky Mountains and the Great Basin, the NWS said. Exposure to such conditions without proper protection can result in frostbite within minutes.

Power outages were expected due to strong winds, heavy snow and ice, and the stress of above-average energy demands.

One of the biggest immediate impacts, even before the storm took full shape, was the disruption to commercial air travel during the busy holiday travel season.

Thousands of flights canceled

More than 5,000 US flights scheduled for Thursday and Friday were canceled, according to flight-tracking service FlightAware, with two major Chicago airports accounting for nearly 1,300 of the cancellations.

The American Automobile Association had estimated that 112.7 million people planned to travel 50 miles or more from home between Dec. 23 and Jan. 2, up 3.6 million travelers from a year earlier and closer to the numbers before the pandemic.

But that number would likely be reduced by air and road travel, complicated by treacherous weather into the weekend.

Even President Joe Biden urged Americans to think twice before heading out after Thursday, calling the gathering storm “dangerous and ominous.”

“This isn’t like a snowy day when you were a kid, this is serious stuff,” he said.

The extreme cold also posed a particular risk to livestock in livestock-intensive regions of the country. Tyson Foods Inc, the nation’s top meat producer by sales, said it has scaled back operations to protect employees and animals.

The Weather Service said relief from deep freezes is on the horizon for the northern Rocky Mountains and High Plains, where the Arctic blast first struck on Thursday. Temperatures in parts of these regions could rise 40 to 60 degrees over the weekend as the cold air mass creeps further east.

The NWS said the “bomb cyclone” was a “once in a generation event” with the power to be deadly. With temperatures of minus 53 degrees Celsius (minus 63 Fahrenheit) in western Canada, minus 38 degrees Celsius in Minnesota and minus 13 degrees Celsius in Dallas, it is already breaking cold records.

It’s snowing even in subtropical northern Florida.

A bomb cyclone or bombbogenesis is a rapidly intensifying storm that occurs when air pressure drops by 20 millibars or more in 24 hours.

This usually happens when a warm air mass collides with a cold one, according to the National Oceanic and Atmospheric Administration.

This time, air from the Arctic rushed into tropical air from the Gulf of Mexico, creating a sink that brought rain and snow.

Breathtaking pressure drop

What makes this storm extraordinary is how quickly the pressure dropped — 40 millibars in 24 hours, according to meteorologist Yann Amice of analysts at Weather’n’co.

“This has led to the development of extreme storm conditions near the core of the low-pressure system with particularly harsh conditions,” said Cyrille Duchesne, meteorologist for the French Weather Channel.

The unprecedented nature of this storm stems from the intensity and extremes of its low temperatures, Duchesne said.

“That makes it extraordinary,” he said.

The storm has triggered a “polar vortex collapse,” with a particularly cold air mass flowing south from the Arctic to lower, warmer latitudes.

The result is a staggering drop in temperature – in Denver, for example, temperatures dropped 90 degrees Fahrenheit in just under seven hours.

Combined with blizzards and snow, the wind chill in regions like the Great Plains can make it feel like minus 55C.

The US National Weather Service warned that such cold weather can cause frostbite on exposed skin, hypothermia, and even death within minutes if exposed to these conditions for too long.

This makes travel of any kind “dangerous” and even “impossible,” she added.

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