The fierce winter weather, part of which was expected to classify as a “bomb cyclone,” was set to pummel parts of Colorado, including Denver, and rapidly intensify throughout the day as it pushes east and north, the National Weather Service said.

Heavy rains turning to snow, blizzard conditions and high winds will affect areas of the country from the Central Rockies across the Plains, and from the Mississippi Valley into the upper Great Lakes, including Wyoming, Nebraska, Kansas and South Dakota.

In Colorado, computer simulations showed a record change in pressure that suggested conditions for the “bomb cyclone,” also known as a winter hurricane.

A storm may become a “bomb” depending on how fast the atmospheric pressure falls; drops in atmospheric pressure are a characteristic of all storms. Barometric pressure must fall by at least 24 millibars in 24 hours for a storm to be called a bomb cyclone.

“It is a huge drop,” Russ Schumacher, a climatologist and professor of atmospheric science at Colorado State University, said in an interview Wednesday. “It speaks to the speed at which the storm intensifies.”

“In terms of the sheer power of the system, I think it is one of the strongest ones we have ever seen in this part of the country,” he added.

The bomb cyclone’s snow and intense winds will create problems associated with blowing gusts of snow and huge drifts, Schumacher said.

The storm was expected to have the greatest impact over a patchwork of territory in different states, including eastern parts of Colorado as well as Nebraska and Kansas, before it moves on and weakens over the next 24 hours.

Schools in Denver, Littleton and several other cities in Colorado were closed, and travel plans were expected to be disrupted across large parts of the state. The visibility will be near zero, the National Weather Service said, with wind gusts of up to 80 mph. Up to 1 foot of snow was forecast on the plains east of the city of Greeley and stretching south to Denver International Airport.

Before noon Wednesday, the Denver airport reported wind gusts of 60 mph, along with heavy snow and quarter-mile visibility.

Snow will probably not accumulate much more than a foot because the storm is moving quickly from one area to another, Schumacher said. People living in the affected areas were likely to have prepared for the storm because forecasts about its approach have circulated for several days, he said.

The Denver airport said it was bracing for several inches of snow and strong winds. Airlines including Southwest, Frontier and United have canceled flights, and more cancellations and delays were possible, the airport said in a statement on Twitter. By late Wednesday morning local time, more than 1,100 flights had been canceled, according to FlightAware.

“These conditions will spread eastward across the plains this afternoon,” the National Weather Service said.

“Travelers across the Colorado mountains and eastern plains should consider canceling travel plans today, as conditions will deteriorate quickly during the late morning or early afternoon,” it added.

By midday Wednesday, parts of Kansas were feeling the fringes of the storm system with a high wind warning, or gusts of up to 60 mph, in the western part of the state, the National Weather Service said.

“Right now Kansas is in the dry part of the system,” said Andy Kleinsasser, a meteorologist with the service in Wichita. “We are getting very strong winds associated with the storm system.”

The storm was tracking along the border between Colorado and Kansas and was expected to veer to the northeast, eventually pushing into Nebraska in the evening and then hitting Iowa, he said.

This article originally appeared in The New York Times.