It marked the second consecutive year that Jutanugarn has claimed a stroke-play medal at a USGA championship, following the 2010 U.S. Women’s Amateur Public Links.

The temperatures continued to rise at Olympia Fields, with Monday’s mid-90s readings giving way to the upper 90s on Tuesday. But as with Monday, the oppressive heat did not faze Jutanugarn in the slightest.

Jutanugarn, a 15-year-old native of Bangkok, followed Monday’s 4-under 68 with a steady round of even par on Tuesday to maintain her position atop the leaderboard at 4-under 140. No other player was even able to break par, with her closest competitor coming in four strokes back at even par.

However, despite her large lead, not everything was up to Jutanugarn’s usual high standards. While she made the turn at one under par and birdied the par-5 10th, consecutive bogeys on the par-4 11th and par-3 12th dropped her back to even for the day.

“On the front nine, I played good,” said Jutanugarn, who competed at the recent U.S. Women’s Open, where she failed to make the cut. “But the back nine was so bad. I missed three short putts from like 3 feet.”

The Jutanugarn family spends five months a year traversing the United States, with Ariya and her sister, Moriya, competing in tournaments. They’ll compete in 12 this summer, and both girls have already claimed victories on the American Junior Golf Association’s summer schedule.

They are a close-knit family, with Moriya, who withdrew from the Girls’ Junior with a wrist injury that she aggravated while competing at this year’s U.S. Women’s Open, on her bag and her parents, Somboon and Narumon, watching from outside the ropes.

“We stay here for five months. If we don’t have [our parents], it would be really boring!” said Jutanugarn with a laugh.

Jutanugarn hopes to better her performance from the 2010 Girls’ Junior, where she lost in the second round of match play in a marathon 25-hole match with Argentina’s Victoria Tanco. But the power game that is stroke play appeals much more to Jutanugarn’s competitive side than the sometimes-cruel luck of match play.

“You don’t know when you’re going to lose,” said Jutanugarn, who admitted to struggling in her past USGA match-play events. “Sometimes, you play good, but you have bad luck and you can lose to a player who’s not so good. Or they’re so good, but you can win if you’re lucky.”

Casie Cathrea, 15, of Livermore, Calif., followed Jutanugarn at even-par 144, carding a 2-under 70 in her morning round. After making the turn at one over on the round, she rattled off back-to-back birdies from within 5 feet on 10 and 11, and tacked on another at the closing par-5 18th to finish with a flourish.

“I just started putting really well, getting it close to the hole and making some putts,” said Cathrea, who advanced to the quarterfinals at the 2009 U.S. Women’s Amateur Public Links at age 13.

Fellow 15-year-old Eimi Koga of Honolulu, Hawaii, recorded the first eagle of the championship at the par-4 11th, sending her 8-iron shot from 130 yards down a hill at the back of the green and into the hole for an eagle-2.

“I was really happy, but it was only the second hole,” said Koga, whose 3-under 69 was the low round of the day. “I kind of wanted it to happen later. But it was a good start.

“I was putting really good. All my putts were going in and I was really happy. That’s what saved me today.”

Koga’s 1-over 145 total gave her sole possession of third place, followed by three players at 2-over 146: 2011 U.S. Women’s Open competitors Mariah Stackhouse, 17, of Riverdale, Ga., and Emma Talley, 17, of Princeton, Ky., as well as Nicole Morales, 15, of South Salem, N.Y. Stackhouse was a member of the Georgia team that won the 2009 USGA Women’s State Team Championship.

The two past U.S. Girls’ Junior runners-up in the field rebounded from poor Mondays to pull clear of the cut line. 2008 runner-up Karen Chung, 16, of Livingston, N.J., converted three birdies en route to a 77-71—148 and a tie for 14th. 2010 runner-up Katelyn Dambaugh, 16, of Goose Creek, S.C., still struggled, but managed a 78-74—152 to tie for 42nd.

Among the players to miss the cut was Tiffany Lim of San Jose, Calif., who advanced to the second round of match play at the 2011 U.S. Women’s Amateur Public Links and returned a 72-hole score at the 2010 U.S. Women’s Open. Arizona’s Julie Yang, who advanced to the round of 16 at the 2011 Women’s Amateur Public Links, was eliminated in the six-player playoff for the final three berths in the match-play bracket.

The 2011 U.S. Girls’ Junior will continue Wednesday with the first round of match play. The second and third rounds will be played Thursday, and the quarterfinal and semifinal matches are on Friday. The 36-hole championship final will be played Saturday.

The U.S. Girls’ Junior is one of 13 championships conducted annually by the United States Golf Association, 10 of which are strictly for amateurs.

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