The Federal Reserve downgraded its outlook for the U.S. economy this year but forged ahead with the phaseout of its signature stimulus program. The nation’s central bank lowered its forecast for growth this year to between 2.1 percent and 2.3 percent, down from its previous prediction of nearly 3 percent. Officials reiterated that they would likely keep interest rates at zero for a "considerable time" after they wrap up their bond purchases later this year. Yellen previously characterized the language as meaning about six months, putting the first rate hike roughly in the middle of next year. But in her session yesterday, she emphasized that the central bank is not locked into a date.