A deep freeze enveloped most of the United States early Friday, while a massive winter storm brewing in the Midwest left two-thirds of the country under extreme weather alerts, confounding Christmas travel plans for millions.
Heading into the 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 New York state and extending north into Canada.
Numbing cold intensified by high winds was expected to extend as far south as the US-Mexico border.
Hard-freeze warnings were posted across the Gulf Coast states of Texas, Louisiana, Alabama and Florida, while significant icing was possible from a separate arctic blast hitting the Pacific Northwest.
By late Thursday, most of the Lower 48 states, from Washington state to Florida, were under wind-chill alerts, blizzard warnings or other winter weather advisories affecting more than 200 million people, about 60% of the population, the National Weather Service (NWS) reported.
The NWS map of existing or impending wintry hazards, stretching from border to border and coast to coast, “depicts one of the greatest extents of winter weather warnings and advisories ever”, the agency said.
The bomb cyclone could unleash snowfalls of 1.25cm per hour driven by gale-force winds, cutting visibility to near zero, the weather service said.
Combined with the arctic cold, wind-chill factors as low as minus 40 Celsius were forecast in the High Plains, the northern Rockies and the Great Basin, the NWS said. Exposure to such conditions without adequate protection can cause frostbite within minutes.
Power outages were expected from high winds, heavy snow and ice, as well as the strain of higher-than-usual energy demands.
One of the greatest immediate impacts, even before the storm fully took shape, was the upending of commercial air traffic during the busy holiday travel period.
Thousands of flights cancelled
More than 5,000 US flights scheduled for Thursday and Friday were cancelled, with two major airports in Chicago accounting for nearly 1,300 of the cancellations, according to the flight-tracking service FlightAware.
The American Automobile Association had estimated that 112.7 million people planned to travel 80km or more from home between Dec 23 and Jan 2, up 3.6 million travellers over last year and closing in on pre-pandemic numbers.
But that number was likely to be diminished by air and road travel complicated by treacherous weather leading into the weekend.
Even President Joe Biden urged Americans to think twice about venturing out after Thursday, calling the gathering storm “dangerous and threatening”.
“This is not like a snow day, when you were a kid, this is serious stuff,” he said.
The extreme cold also posed a particular hazard to livestock in ranching-intensive regions of the country. Tyson Foods Inc , the nation’s leading meat producer by sales, said it had scaled back operations to protect employees and animals.
The weather service said relief from the deep freeze was in sight for the northern Rockies and High Plains, where the arctic blast first materialized on Thursday. Temperatures in parts of those regions could rebound by 40 to 60 degrees over the weekend as the cold air mass creeps farther east.
The NWS said the “bomb cyclone” was a “once in a generation type event” with the power to turn deadly. It is already breaking cold-weather records, with temperatures falling to minus 53 degrees Celsius (minus 63 Fahrenheit) in western Canada, minus 38C in Minnesota and minus 13C in Dallas.
It’s even snowing in subtropical northern Florida.
A bomb cyclone, or bombogenesis, is a quickly intensifying storm that occurs when air pressure drops 20 millibars or more within 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 ploughed into tropical air from the Gulf of Mexico, forming a depression bringing rain and snow.
Stunning pressure drop
What makes this storm extraordinary is just how fast the pressure dropped — 40 millibars in 24 hours, according to meteorologist Yann Amice of analysts 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, a meteorologist from the French Weather Channel.
The unprecedented nature of this storm comes from the intensity and extremity of its low temperatures, Duchesne said.
“That’s what makes it exceptional,” he said.
The storm has sparked a “polar vortex plunge” where a particularly cold air mass from the Arctic heads south toward the lower, warmer latitudes.
The result is a vertiginous drop in temperatures — in Denver, for example, temperatures dropped 33 degrees Celsius in barely 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 can lead to frostbite on exposed skin within a matter of minutes, hypothermia and even death if exposed to these conditions for too long.
This makes travel of any kind “dangerous” and even “impossible”, it added.
