Three tornadoes were spotted in Big Stone County in far west-central Minnesota on Wednesday afternoon.

One was spotted 4 miles northwest of Clinton at 3:42 p.m., another 4 miles south of Barry at 3:46 p.m. and another in Ortonville.

The extent of the damage is unknown, but early reports indicated the roof of an outbuilding was blown off in an area where weather officials suspect a tornado formed.

That one was about 10 miles east of Wheaton in neighboring Traverse County, according to Dan Mohr, lead meteorologist at the National Weather Service (NWS) in Aberdeen, S.D.

"We had an unusually strong upper low-pressure system that came through," said Mohr.

He added the mix of warmth, a cold front and already strong winds created the right conditions for the tornadoes to form.

"It was a decent environment for these storms to develop and produce some spin-ups," he said.

Tornadoes occur in the fall in Minnesota, though they happen more often in the spring and summer months, said Joe Calderone, senior forecaster at the NWS in Chanhassen.

Tornadoes are rare in October in Minnesota. As the cold sets in, the state will gradually see less and less until next year.

"The cooler we get the less likely we're going to see these systems," Calderone said.

Alex Chhith • 612-673-4759