Investors should expect U.S. stocks to inch higher next year as economic growth moderates and the effects of President Donald Trump's tax cuts dwindle, according to RBC Capital Markets.

Chief equity strategist Lori Calvasina wrote in her 2019 outlook on Thursday that the broad index should post more muted gains as gross domestic product growth recedes toward its normal rate, assuming no additional fiscal stimulus.

"Our preliminary forecast/base case is for the S&P 500 to end 2019 near 2,900, up 6 percent from the Nov. 28 close, and in line with the median gain in the S&P 500 during years that precede 0 to 2 percent real U.S. GDP years," Calvasina wrote. The firm sees 2019 S&P earnings per share at $171 next year.

Her year-end 2019 S&P target is shy of the median 3,000 forecast of 10 other equity strategists surveyed by CNBC, though more strategists are expected to issue forecasts in the coming week and could impact her ranking.

A growing number of Wall Street firms believe U.S. GDP growth will contract to around 2 percent by 2020 from current levels above 3 percent. RBC Capital sees GDP climbing less than 2 percent in 2020 but believes that if recession fears mount before then, stock returns could be even worse.

"The economy itself is currently quite strong. But investors have been preoccupied with the idea that it is 'late cycle' and this longer-term worry has been driving positioning and performance," the strategist added. "We do not believe a recession is on the horizon, but if we are wrong, downside moves could be much more meaningful."