Winther, 33, got off to a slow start, struggling to a bogey on the first before making five birdies as he went out in 31. The Dane continued his fine form into the back nine, carding five more birdies and a bogey to match the lowest round of his European Tour career.
The 33-year-old is seeking his first Tour win in his 179th start.
On a tight leaderboard, the top 26 players are separated by just four shots going into Friday’s second round.
Information from the Associated Press contributed to this report.