Economists sharply lowered their forecasts for employment and economic growth in the first quarter in a new Wall Street Journal survey, after recent government data suggested the U.S. economy is cooling.

Private-sector economic forecasters surveyed in recent days expect U.S. economic output to grow, on average, at a 1.3% pace in the first quarter. That is a sharp drop from the last survey, in early February, when they predicted a 2% growth rate for the January-to-March period.

If...