An intense and ferocious winter storm — a "bomb cyclone" — is expected to bring hurricane-force wind gusts, blizzard conditions and a flood threat across a swath of the U.S. heartland Wednesday.
A bomb cyclone happens when there's a rapid pressure drop, with a decrease of at least 24 millibars (which measures atmospheric pressure) over 24 hours known as bombogenesis. This storm has dropped 27 millibars since Tuesday morning and continues to strengthen.
The current pressure in the storm is equivalent to what you would typically find in a Category 1 hurricane, said CNN Meteorologist Brandon Miller. Further pressure drops later Wednesday should bring it to Category 2 equivalent.
The massive storm is expected to wallop several areas including the Rockies, central and northern Plains and the Upper Midwest with blizzard conditions and winds that could blow up to 70 mph. Other hazards include heavy snow and severe storms with possible tornadoes and flooding.
Blizzard and winter storm warnings are in effect for portions of Colorado, Wyoming, Nebraska and South Dakota. Heavy snow is expected in portions of the Rockies and northern Plains, including Denver into Thursday.
Watches, warnings and advisories for the storm cover about 1.5 million square miles, which is roughly half of the area of the continental US — and they stretch from the Mexican border to the Canadian border.
Travel will be dangerous, if not impossible, at times, across areas where the blizzard warning has been issued. Severe storms capable of producing damaging winds, hail, and tornadoes are forecast from the southern Plains and into the Mississippi River Valley. More than 55 people million are under a high wind threat; more than 10 million are under winter storm threats; and more than 17 million are under a flood threat.
The National Weather Service in Boulder, Colorado, issued a blunt message Tuesday: "Please cancel any travel plans Wednesday afternoon and evening especially east of I-25, and stay tuned for further updates!"
It warned of icy roads, whiteout conditions and strong winds.
"The heavy snow and visibility near zero will create extremely dangerous travel conditions, and power outages are also possible," according to the weather service.
What raises a common winter storm to the level of 'bomb cyclone'? It's all about rapid, sharp changes in atmospheric pressure – and the scientists who coined the term meant to highlight their power.
Travel and schools affected
More than 1,400 flights had been canceled by Wednesday morning, according to FlightAware. The majority of those cancellations were flights destined for or originating at Denver International Airport (DIA), where a blizzard warning is in effect.
Denver itself is expected to get snow accumulations of about 5 to 8 inches on Wednesday.
Multiple Colorado school districts were closed Wednesday. That includes the Denver Public Schools, which cited "severe weather and road conditions."
Wyoming had closed state offices in Cheyenne, while South Dakota's governor ordered state offices closed in 39 central and western counties due to the storm.
In Nebraska, officials late Wednesday morning closed a roughly 130-mile strech of westbound Interstate 80, from Ogallala to the state line with Wyoming, because of the blizzard.
Thunderstorms across portions of the southern Plains will make way on Wednesday for sustained winds of 35 to 45 mph, akin to the strength of a low-end tropical storm.
Gusts up to 110 mph
Wind gusts of 50 to 70 mph are expected Wednesday afternoon through Thursday morning across Colorado, New Mexico, Texas and Oklahoma, CNN meteorologist Monica Garrett said. Some areas could see gusts as strong as 110 mph.
The storm is forecast to rapidly intensify overnight Wednesday east of the Colorado Rockies and trek slowly northeast through Thursday, bringing a variety of extreme weather from New Mexico to the Midwest. Snow is expected to taper off by midday Thursday, but strong winds may persist through the evening.
In addition, flood watches have been issued across the Midwest and Great Plains amid concerns that heavy rains will melt snowpack and trigger significant flooding. Flash flooding is possible if ice jams clog rivers and streams, the weather service noted.