The storm that slammed into Story City and the surrounding area, knocking down trees and tearing parts of a building off in the city’s industrial park, was the result of straight-line winds of up to 90 mph, officials with the National Weather Service in Des Moines said Monday.

The storm struck just before 7:30 p.m. Friday as a strong system swept across the area, bringing severe storms and gusty winds to the region. The system ushered in much colder weather, which led to snow on Saturday and Sunday. But it was the storm Friday night that left questions about the cause of the damage, with many residents saying they saw a funnel cloud or tornado around the time the storm struck.

Mike Fowle, a meteorologist with the National Weather Service in Des Moines, said the agency reviewed data from the event, including atmospheric conditions and radar data as the storm roared through. It also reviewed damage reports, and upon analyzing all the information determined the “most plausible” cause of the damage was straight-line winds. A severe thunderstorm warning was in effect at that time for strong winds capable of producing damage.

“There was a microburst right in that area near Story City at about that time, and wind speeds were in the 80 to 90 mph range,” Fowle said.

As far as reports of a tornado by several residents on social media, Fowle said what they likely saw was the result of a strong east wind ahead of the storm front colliding with winds from the west and northwest as the front passed, causing some swirling.

“There wasn’t a longer living circulation going on,” that would have been needed for the formation of a tornado, Fowle said.

He said radar showed a very linear pattern of storms, without the signature hook echo indicating rotation that could lead to a tornado.

He also said people may have seen the shelf cloud and low hanging scud clouds as the storm moved through, mistaking those for a funnel cloud.

Tyler Faaborg, who was visiting his parents’ farm six miles north of Roland, east of Story City, said he believes it was a tornado that struck the area, including his parents’ farm, where an old cattle barn collapsed with debris blown three-quarters of a mile away.

“It’s my fifth one I’ve seen so I have a little experience with them,” Faaborg said. “It was definitely a tornado. Not a well-defined one, but it was definitely a tornado.”

He described it as wide and weak and moving up and down as it swept across his parents’ farm.

“The winds picked up pretty good, enough to get my attention, and I looked out a window to the east … coming straight our way, going southwest,” Faaborg said.

It missed the house, he said, but blew up enough dust he couldn’t see more than 20 feet out the window.

Inside the destroyed cattle barn was equipment being stored there by a friend, who rents the space from Faaborg’s parents. The machinery included a combine, some wagons, a sprayer, a planter and grain cart, which had flipped upside down, he said.

Three other older buildings crumbled under the force of the wind. The only damage to the house were the shingles on its roof, Faaborg said.

The whole experience lasted just 10 to 15 seconds, he said.

Another resident, Justin Schultz, of Story City, was among those who reporting seeing a tornado Friday night.

“In 2001 or 2002, I was in the huge tornado that hit Agency, Iowa,” he said. “So I’ve been in a tornado before, and I know what one looks like. And this was a tornado.”

Schultz said he and his wife Christina were driving from Roland to Story City when they saw a funnel cloud a mile or so outside of Story City.

“My wife recorded the funnel cloud crossing the road behind us,” Schultz said. He pulled the car over and turned it around so they could see the funnel better.

“I watched it drop. I watched it hit the ground and pick up debris,” Schultz said. “It was several hundred feet wide when it hit. It was only on the ground for maybe 15 to 20 seconds.”

It was so surreal, it seemed like a scene from a movie, he said.

“But it was real. And I watched it,” he said.

In Story City, the brunt of the damage occurred in the city’s industrial park, where portions of two walls at the NextEra wind turbine repair facility were torn away, exposing the interior to the elements, while other parts were heavily warped. The roofs also sustained damage.

NextEra spokesman Steve Stengel said the company was assessing the damage to the main repair facility and the warehouse on Monday, but it was too early to give a damage estimate. He said the building’s electric and gas connections were not harmed during the storm.

“It’s unclear at this point when the facilities will resume normal operations,” he said.

Story County Emergency Management Coordinator Keith Morgan said the most severe wind damage was “very spotty” across the city and concentrated mostly to the east side near the NextEra Energy campus and 550th Avenue in the southwest corner of town, where several utility poles were downed.

Morgan said Monday it wasn’t clear yet what the monetary costs of damage might be. No injuries were reported.

To the west, on U.S. 69, Slim’s Country Market sustained damage to its roof, while a beam holding up an awning broke in the front of the building. Owner Kurt Johnson said the damage wasn’t as bad as it could have been.

“You always think the worst, but we should be able to get cleaned up and open here in a week or so,” he said.

Story City Administrator Mark Jackson said besides the damage at the NextEra plant, most other damage in town consisted of a few large trees that were toppled. Photos posted on social media also showed a shed blown over against a fence. Damage to farm buildings was also reported between Boone and Ames, north of U.S. Highway 30.

“It had the potential to be a lot worse,” Jackson said.