Nobody was hurt, but three commercial buildings, all of them used for storage, were damaged, McMinnvilleFire Chief Rich Leipfert said. The porch roof on one nearby home also sustained minor damage, Leipfert said.
A two-person NWS storm survey team dispatched to the scene confirmed the damage was caused by atornado.
The tornado's estimated top winds in the most damaged area ranged from 86 to 90 miles per hour, Weather Service meteorologist Treena Hartley said late Thursday night. That puts it in the EF1 storm category.
Elsewhere it was defined by the damage found as an EF0. That class of storm has winds from 65-85 mph, Hartley said.
McMinnville is about 35 miles southwest of Portland.
"I was just across the way and I saw the whole roof roll up off of the building," Kelly McDonald, managing partner of a nearby development, told the Yamhill Valley News-Register. "I wish I'd had the presence of mind to take a picture. I was just trying to get everyone inside."
Sean Cahill got caught in a torrential hailstorm as he was driving. He didn't see any cloud, he said, but he did see building debris flying in circles about 100 feet in the air.
"It looked like a confused flock of birds," Cahill said.
Experts look at debris patterns to confirm whether a tornado is responsible for damage, meteorologist Miles Higa said. The survey team also reported some damaged trees near the buildings that were hit.
The McMinnville tornado hit at about 4:30 p.m., he said.
Funnel clouds reportedly were also seen Thursday afternoon in or near the communities of Hillsboro, Albany and Harrisburg, Higa said.
Tornadoes in Oregon are rare. The last notable twister struck Aumsville, east of Salem, in December 2010, according to a list on the National Weather Service website. The storm caused more than $1 million in damage to 50 homes and four businesses, but nobody was injured.