Shane Lowry hit a six-under-par 64 to move into a share of ninth place at the Wyndham Championship in Greensboro, North Carolina.

Lowry hit three birdies and one bogey on the front nine, before posting four further birdies on a flawless back-nine to reach nine under par after the second round at the Sedgefield Country Club. 

The Clara native sits four shots behind leaders Webb Simpson and Ryan Armour, with the latter shooting a stunning nine-under-par 61 on the second day of the tournament. 

Lowry currently sits in 145th position in the Fed Ex Cup standings and has yet to record a top-ten finish on the PGA Tour this season. 

A career best nine-under 61 lifted Ryan Armour into a share of the lead alongside Webb Simpson.

Armour and Simpson are level at 13 under, one shot ahead of Henrik Stenson and two clear of Ollie Schniedarjans and Vaughn Taylor.

But the day belonged to Armour, who recorded nine birdies - including four in a row from the fifth to the eigth - on his blemish-free scorecard.

Armour came into the weekend 187 on the points list, still a long way off the top 125 who will advance to the post-season.

"I think the play-offs started a long time ago for me," he said. "I listed some goals, both personal and professional on Monday, which I hadn't done all year, for the week.

Elsewhere, Padraig Harrington shot another under par round to move to six under for the tournament and sit in a share for 27th going into the weekend following his 68.

Languishing in 199th position, Harrington needs to either win the tournament or finish second to retain his PGA Tour card for 2018, though he does have a medical exemption following back surgery in March which will entitle him to play in nine tournaments next year should he miss out this weekend. 

With his rivals burning up the course, Harrington will need to shoot very low rounds on Saturday and Sunday. 

Meanwhile, Waterford's Seamus Power needed a par on his final hole to stay in the tournament and maintain his own fight to stay inside the top 125, which will see him retain his card for 2017-18, while also securing his place in the end-of-season play-offs.

Power overcame a nervy finish, where he bogeyed three of the last six holes to squeeze through to the weekend in North Carolina.

However, he secured par and looks set to be around for the weekend. He hit an even par round of 70 on the Friday. 

Graeme McDowell hit a second round of 68 to reach -1 for the tournament but missed the cut by two shots and will not be around for the weekend.