CHICAGO -- A massive storm with wind gusts up to 81 mph howled across the nation's midsection Tuesday, snapping trees and power lines, ripping off roofs, delaying flights and soaking commuters hunched under crumpled umbrellas.
Spanning from the Dakotas to the eastern Great Lakes, the unusual system mesmerized meteorologists because of its size and because it had barometric pressure similar to a Category 3 hurricane, but with much less destructive power.
Scientists said the storm had the force of a blizzard minus the snow.
"If it were colder, we'd have a blizzard with this system," said David Imy, operations chief at the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman, Okla. But temperatures were in the 50s and 60s, instead of the 20s.
The National Weather Service said the system's pressure reading Tuesday was the lowest ever in a non-tropical storm in the mainland U.S. If confirmed, that would be worse than the pressure that produced the Blizzard of 1978, the March 1993 "Storm of the Century" or the November 1975 storm that sank the Edmund Fitzgerald freighter, memorialized in a song by Gordon Lightfoot.
The storm blew in from the Pacific Northwest on the strength of a jet stream that is about one-third stronger than normal for this time of year, Imy said. As the system moved into the nation's heartland, it drew in warm air needed to fuel thunderstorms. Then the winds intensified and tornados formed.
Add to that the fact the storm was moving fast, 50 to 60 mph, and the winds became even stronger, Imy said.
By Tuesday morning, sustained winds were about 35 to 40 mph. A gust of 81 mph was recorded in Butlerville, Ohio, and 80 mph in Greenfield, Ind., according to NOAA.
At one point, more than 145,000 homes and businesses were without power in Wisconsin, Indiana, Illinois, Ohio and the St. Louis area.
The storms were headed toward the East Coast by late Tuesday afternoon. Weather service meteorologist Charles Mott said the winds might weaken, but a squall line was moving ahead of the storm, causing more tornado warnings.
A tornado touched down in Racine County, Wis., where two people were injured when a section of roof was torn off a tractor factory, and in Van Wert County, Ohio, near the Indiana border, where a barn was flattened and flipped over a tractor-trailer and camper. A tornado also touched down in Peotone, Ill., where three people were injured when a home's roof came off, and twisters were suspected in several other states.
Sheryl Uthemann, 49, was working first shift at the Case New Holland plant in Mount Pleasant, Wis., when the storm blew through about 8 a.m. and started to lift the roof.
"It was just a regular workday and all of a sudden that noise just came and (co-workers) said 'Run! Run! Run!' You didn't have time to think," she said. "I looked up where the noise was coming from and saw pieces of the roof sucked up. I've never been more scared, ever."
In the Indiana town of Wanatah, about 60 miles southeast of Chicago, a pole barn at a hydraulics company was destroyed, and two homes were severely damaged, though no injuries were reported.
Firefighter John Sullivan said he saw a funnel cloud, but it did not touch down.
In the Chicago suburb of Lindenhurst, a woman was injured when a branch fell about 65 feet from a large tree, crashed into her car and impaled her abdomen. She was taken to a hospital in fair condition, authorities said.
Meteorologists said the storm's barometric pressure readings were comparable to those of a Category 3 hurricane but with much weaker winds. The wind gusts were only as strong as a tropical storm. Category 3 hurricanes have winds from 111 to 130 mph.
Storm pressure works like this: The lower the pressure, the greater the winds. The higher the pressure, the calmer and balmier the weather is. If Tuesday's low-pressure system had been over water -- where winds get higher -- it would have created a major hurricane, Imy said.
Tom Skilling, a meteorologist with WGN-TV in Chicago, said the size of the storm -- 31 states were under some sort of whether advisory, from blizzards to thunderstorms to tornadoes -- also was unusual.
Severe thunderstorm warnings blanketed much of the Midwest, and tornado watches were issued from Arkansas to Ohio.
Eleven states were under a high wind warning: Illinois, Wisconsin, Indiana, Iowa, Michigan, North Dakota, South Dakota, Nebraska, Minnesota, Ohio and parts of Kentucky. The weather service said the winds would subside Tuesday evening but could pick up again on Wednesday.
Meanwhile, much of North Dakota was under a blizzard warning. The weather service said up to 10 inches of snow could fall in some areas into early Wednesday across North Dakota and into northern South Dakota. Wind gusts of more than 50 mph in many areas would make travel treacherous.
In the Chicago area, morning commuters faced blustery, wind-driven rain as they waited for trains. Some huddled beneath railway overpasses to stay out of the gusts, dashing to the platform at the last minute.
About 300 flights were canceled and others delayed at O'Hare Airport, a major hub for American and United airlines. The storms also disrupted flights at the Cincinnati, Indianapolis and Minneapolis airports.
Chicago's 110-story Willis Tower, the nation's tallest building, closed the Skydeck observatory and retracted "The Ledge" attraction -- four glass boxes that jut out from the building's 103rd floor.
In Michigan, wind speeds topped 35 mph on the five-mile Mackinac Bridge, which links the state's Upper and Lower peninsulas. Traffic continued to cross, but escorts were given to "high-profile" vehicles such as large trucks, school buses and vehicles towing trailers.
In St. Louis, strong winds were blamed for a partial building collapse that sent bricks, mortar, roofing and some window air conditioning units raining down onto a sidewalk. No one was injured, and officials were inspecting the 1920s-era building.