Economic bellwether FedEx Corp (FDX.N) rose 2.4 percent to $91.31, lending support to the market after the shipping group reported strong fourth-quarter profit and forecast robust 2012 earnings.
"The new news there is FedEx made noise about how the cost of doing business is going down as opposed to up. So are we starting to see some slowdown in inflation here?" said Stephen Massocca, managing director at Wedbush Morgan in San Francisco.
The Dow Jones Transportation average (.DJT) gained 0.8 percent.
The Dow Jones industrial average (.DJI) gained 4.39 points, or 0.04 percent, to 12,194.40. The Standard & Poor's 500 Index (.SPX) put on 1.74 points, or 0.13 percent, to 1,297.26. The Nasdaq Composite Index (.IXIC) added 2.13 points, or 0.08 percent, to 2,689.39.
The Fed is likely to acknowledge weakness in the economy and reiterate its commitment to keeping interest rates low for an extended period, according to analysts.
Investors will look for clues on new measures to support the economy as the Fed's second quantitative easing program ends this month.
"(Bernanke) could surprise you, but he's certainly not looking at inflation or looking at an overheating economy. He's not looking at an economy that is so dire that he has to fire a bullet he really doesn't want to fire right now. So it's going to be the bullet is in the gun, it's ready to go if I need it, and everyone is expecting that," said Massocca.
Adobe Systems Inc (ADBE.O) slumped 6.4 percent to $29.96 a day after the software maker reported a 54 percent jump in quarterly profit but warned of weakness in European demand.
U.S. stocks advanced for the fourth straight day on Tuesday on expectations the Greek prime minister would survive a confidence vote, a key hurdle to avoiding a debt default, adding momentum to a recent rebound.
The Nasdaq posted its biggest percentage gain since October on Tuesday, while the S&P 500 marked its best day in two months in what traders see as continued short-term buying from deeply oversold levels.
Net short positions by hedge funds on the S&P 500 have recently increased, according to Societe Generale cross-asset research.
A statement from the Federal Open Market Committee is due at 12:30 p.m. EDT, followed by Bernanke's press conference at 2:15 p.m. EDT.
(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)