A potential fourth increase would be motivated by rising concerns about an overheating economy, with such low unemployment that it sets off an inflationary spiral as companies lift wages to compete for scarce workers and increase prices to pay for those higher salaries. A portion of the voting membership of the committee rotates every year among the Fed’s regional bank presidents. The new members tend to worry more about inflation than those they replaced. Even some members who have fretted more about growth than inflation appear to be shifting their calculus.

Lael Brainard, a Fed governor who has been less hawkish than many of her colleagues, said in a speech this month that in many ways, “today is the mirror image of the environment we confronted a couple of years ago.”

“In the earlier period, strong headwinds sapped the momentum of the recovery and weighed down the path of policy,” she added. “Today, with headwinds shifting to tailwinds, the reverse could hold true.”

A Case for Caution

If the Fed sticks to three planned rate increases this year, analysts will point to lingering uncertainties in the recovery, including structural issues like a ballooning debt load and trade barriers that could turn the economy’s tailwinds back into headwinds.

Recent data suggest that economic growth is falling short of expectations for the first quarter. Wage growth appears to be improving, but the signs are mixed. Markets have been rattled in recent weeks by Mr. Trump’s tariff plans and embrace of a potential trade war. The Fed seems unlikely to react strongly to any one of those factors, but taken together, they could prod officials into pushing any additional rate move into 2019.

Powell’s Big Performance

Though this will be his first news conference as Fed chairman, Mr. Powell has already faced tough questioning during two days of congressional hearings in February and March. He struck a careful tone in those appearances, saying he had upgraded his own economic outlook but saw no evidence yet of overheating in the economy.

Mr. Powell also offered only gentle criticism of Mr. Trump’s planned tariffs on imported steel and aluminum. He praised free trade in general, while acknowledging that it had hurt some workers by shifting jobs overseas, and added, “The best approach is to deal directly with the people who are affected rather than falling back on tariffs.”