A “very unusual” tornado that was first reported Tuesday morning along the Interstate-5 corridor has been confirmed as a tornado of the week, the National Weather Service said Wednesday.

The storm moved north at 10 mph and was located about 35 miles (55 kilometers) south of Pittsburgh, the Weather Service reported.

The tornado was initially reported to be a severe weather advisory but was upgraded to a tornado threat.

It moved northeast, then east, then southeast to pass over the area near Altoona, Pa., about 20 miles (32 kilometers) north of Pittsburgh.

Tornado warnings were issued for eastern and western Pennsylvania for more than an hour Wednesday afternoon.

“It’s a very unusual storm, with a lot of wind shear and the winds were really strong,” said Bill Davenport, a meteorologist for the National Hurricane Center in Norman, Okla.

“We’re still assessing the impact.”

The National Weather Services Office of Emergency Management said the tornado was located in a storm system known as a severe thunderstorm.

The area is currently under a tornado watch.

The weather service also reported a tree collapse in the Pittsburgh area Wednesday afternoon, with damage estimated at $1 million.

“The damage in this area is very significant, but we do not have a number yet,” the weather service said.

Davenfield said the area was being heavily impacted by the storm.

“There’s a lot that’s going on, so we don’t know yet if the trees are going to be destroyed,” he said.

A storm surge warning is in effect for parts of the Allegheny region, including Westmoreland County, and a tornado warning was issued for the entire state.

A tornado warning remains in effect in western Pennsylvanian, but a “very large tornado” is no longer a tornado, according to the weather agency.

The Associated Press contributed to this report.