GREENSBORO — N.C. State sported new warmup shirts for the ACC tournament Thursday.

"Impossible is nothing" it read on the front and "Wolfpack in the House" on the back. Both slogans proved to be true after State's 59-57 upset of No. 6 Clemson to move into today's quarterfinals.

The 11th-seeded Wolfpack did what previously had been impossible, beat a big, athletic Clemson team for the first time under coach Sidney Lowe, ending a five-game losing streak in the series. In the process, State (18-14) extended its season to tonight's matchup with No. 3 Florida State.

Tracy Smith scored 19 points to lead State to its fourth win in five games after a 3-10 ACC start. While fellow Big Four rivals Wake Forest and North Carolina bowed out on Thursday, the Wolfpack will, as the shirt said, be in the house today.

"It's an experience like they've never seen," Lowe said.

It was a freshman, Richard Howell, in his first tournament game, who made the most of the experience. The burly forward, who has been hampered by injuries in his first season, cleared out 11 rebounds and scored nine points, none bigger than a tip-in at 2:18 to extend the Pack's lead to 55-47.

Clemson (21-10), with 17 points from Trevor Booker, scrambled to make it 57-54 with 10.5 seconds left, but a pair of free throws by C.J. Williams proved to be the difference.

After Demontez Stitt hit a 3-pointer with 4.1 seconds left, Clemson never got the ball back for a chance to win.

With its sixth win over a team likely to make the NCAA tournament field, State likely extended its season beyond today's quarterfinals and into the 32-team NIT field. The Pack hasn't been to the postseason since 2007 and hadn't won an ACC tournament game since then, either.

"We're getting better," Lowe said. "The guys are really starting to buy in."

State showed resilience and poise in its first ACC tournament win since the 2007 semifinals. The upset almost unraveled on a four-point possession by the Tigers at the 9:54 mark of the second half.

With State up 44-37, Farnold Degand was whistled for an intentional foul on Booker. The All-ACC forward hit one free throw, and then Noel Johnson drained a 3 from the left corner to cut what was a 10-point lead to 44-41.

The Pack had coughed up second-half leads during the regular season against Virginia, Maryland and North Carolina. But this time, Lowe wasn't worried history would repeat itself.

"No, I didn't [think we'd lose] because we can't allow one play to change the momentum of the game," Lowe said.

State didn't. Scott Wood's 3-pointer at 8:41 gave the Pack a little room and a 47-41 margin. Smith's tip-in follow of a Dennis Horner miss made it 49-41.

"We had battled off all of their runs," Wood said.

One of the main reasons State had been winless against Clemson under Lowe was it couldn't handle the Tigers' press.

There were turnovers by the Pack, 19 in all, but it was able to neutralize the Tigers' press, despite missing point guard Javier Gonzalez for more than 9 minutes in the first half. Gonzalez twisted his right ankle at the 16-minute mark and left for the locker room.

"We were patient and we were aggressive," Gonzalez said. "Everybody was getting to the ball."

With and without Gonzalez, State got steady ballhandling from guard Julius Mays and bonus production Howell to take a 25-21 halftime lead. He helped offset Clemson's size, holding Booker and Jerai Grant to a combined seven points in the first half.

The last time Howell saw Clemson, he had a potential game-winning shot blocked by Grant in the final seconds. He didn't forget that encounter.

"I definitely remember," Howell said. "This was my statement game. I wasn't going to allow that to happen again."

It didn't, and State's season will last another day.

jp.giglio@newsobserver.com or 919-829-8938