HARRISON, N.J. -- There was a good reason D.C. United wanted to play the second leg of the Eastern Conference semifinals in a driving snowstorm Wednesday.

Those conditions suited a scrappy team that knew it needed every ounce of luck to extract a victory over a team with more refined and plentiful attacking weapons.

But the snow the day before, which forced the game's postponement, had nothing on the storm of events that took place midway through the second half Thursday at Red Bull Arena. It finished with United scratching out a 1-0 win on the night and a 2-1 edge over two games to reach the conference final in its first playoff appearance since 2007.

"It's been crazy," United backup goalkeeper Joe Willis said. "It's funny because it feels like we've been playing real well. We've been winning a lot of games, but it feels like a roller coaster ride. It's had its ups and downs. Sometimes you get that feeling like it's you against the world."

It began when New York forward Kenny Cooper was put through on goal and clipped by a diving Bill Hamid. The United starting goalkeeper was given a red card and the Red Bulls a penalty kick in the 69th minute.

Cooper converted his shot, but referee Mark Geiger called for a rekick after encroachment by a number of New York players -- the same call he made against D.C. United in August. Fresh off the bench, Willis, beaten down the middle the first time, dove to his left to stymie Cooper on the second try.

"I don't know how you do that, how you come on in a playoff game of that magnitude and make that big of a save to keep us in the game," United's Chris Pontius said.

United's man disadvantage was erased when New York defender Rafa Marquez picked up a second yellow card in the 75th minute.

Robbie Russell, making his first start for United since July in place of suspended Andy Najar, found rookie Nick DeLeon behind the New York defense for the series winner in the 88th minute.

Red Bull Arena was nothing like the day before, when the stadium was buried underneath a nor'easter snowstorm. Sheltered from the winds, the playing surface was smooth and pristine. Even the snow along the sideline was gone, leaving no lingering signs of the frantic and futile attempt to clear the field the night before.

The intensity and urgency of both teams was captured in the 28th minute, when United miraculously staved off one of New York's best chances of the game. Hamid made the initial save on Thierry Henry's shot from the top of the box. But when the ball popped up, Hamid was unable to pull it down or punch it clear. It fell back to Henry, whose second attempt was blocked by Dejan Jakovic. United wasn't out of danger until Joel Lindpere's effort spun just off target.

The pressure increased on United in the second half. Henry's dangerous counterattack ended with the ball rolling harmlessly across the goal, similar to his header moments later. Hamid then denied Dax McCarty from point-blank range after a Tim Cahill header.

"[Hamid] kept us in that game," United coach Ben Olsen said. "When he stands up and plays big and doesn't guess, he's a very strong goalkeeper, and he keeps us in games. He's done that all year."

United advanced to meet the Houston Dynamo in the first of a two-game series that starts Sunday in Texas at BBVA Compass Stadium.