Zach Johnson and Craig Lile share third place 8-under-par 208. Johnson, one of the hottest players on tour, is seeking his fourth straight top-four finish.
The field has had to battle the weather all week. Saturday's action saw wind gusts of up to 30 mph and wind chills in the 40s. Sunday's forecast calls for wet weather most of the day.
'Mentally this is really tough weather,' said Long. 'Par is a good score on a day like this.'
Isenhour began the day five shots off the pace and had an up-and-down start to his round. He opened with a birdie at the par-4 first when he stuck a sand-wedge within a foot. After finding the rough off the tee at the next, he was unable to save par.
Isenhour, who won the BMW Charity Pro-Am at The Cliffs two weeks ago, rolled in a six-footer for birdie at the third. He again followed with a bogey when he was unable to sink a five-foot par save at the fourth.
'I hit some squirrelly shots on the first four holes, but then I hit it really solid the rest of the way,' Isenhour said. 'I was able to stay patient.'
He settled down from there. Isenhour sank a three-footer for birdie at the par-3 seventh and two-putted for birdie at the par-5 eighth.
Around the turn, Isenhour holed a pitching-wedge from 120 yards out at the par-4 11th for eagle.
'I hit it perfect,' Isenhour said of his pitching-wedge. 'I knew it was going to be good, but to hear it rattle in was nice.'
He closed with birdies at 15 and 17 to grab a share of the lead. He also made a 10-foot par save at the last.
'I made the key putts today and that is what I've been doing lately,' said Isenhour. 'When you are going well, it seems like you make the putts like I made on 18.'
Long started his round one shot behind overnight leader Fran Quinn. Long got his round going with a 10-foot birdie putt at the par-3 third. He later two-putted for birdie at the par-5 eighth.
On the back side, Long rolled in a six-footer for birdie at the par-5 12th to get to minus-10. However he could not save par at the last and fell into a tie for first.
'I tried to be patient all day,' said Long. 'It was tough reading putts today with the winds gusting. I tend to play reasonably well in the wind.'
Eduardo Herrera and Blaine McCallister share fifth place at 7-under-par 209. Quinn, Vaughn Taylor, Roland Thatcher, Omar Uresti and Russ Cochran are one-stroke back at minus-6.