President Donald Trump speaks about the economy on the South Lawn of the White House on July 27, 2018, in Washington, DC. Nicholas Kamm | AFP | Getty Images

Respondents to the CNBC Fed Survey foresee good times for the economy and the stock market, but they have put an asterisk next to those predictions because of growing concerns over a trade war and monetary policy. Growth year over year is seen rising nearly 3 percent in 2018, before dropping to 2.7 percent in 2019, and the is expected to rise about 6 percent by year-end. Inflation is seen staying low along with the unemployment rate, and the yield on the 10-year Treasury note will rise only to 3.5 percent by the end of 2019. "Goldilocks is alive and well," wrote Marshall Acuff, managing director at Silvercrest Asset Management, in response to the survey. But several significant clouds hang over most forecasts. Almost two-thirds of the 42 respondents, including economists, money managers and strategists, see the recent economic strength as temporary. And 53 percent peg protectionist trade policies as the biggest threat to the economy. While 59 percent approve of President Donald Trump's handling of the economy, an equal percentage say his trade policies will reduce economic growth, and 54 percent say it will reduce employment.

Wouldn't take much to derail

"While the U.S. economy still has solid growth potential in front of it, you still get the sense that it wouldn't take much to watch it derail, with a high degree of confidence that Washington will be the cause of the derailment with its trade policies or some poor decision-making at the top," said Kevin Giddis, head of fixed income capital markets, Raymond James Financial.