NEW YORK—Wall Street advanced on Friday as Federal Reserve Chairman Jerome Powell’s remarks at the Jackson Hole Symposium calmed fears over the tapering timetable and sent investors into the weekend in a buying mood. All three major U.S. stock indexes extended their gains after Powell’s statement was released, and put the S&P 500 and the Nasdaq on track to notch record closing highs. All three indexes were set to post weekly gains. In his prepared remarks, Powell stopped short of providing a clearer picture regarding the timing of the central bank’s tapering of asset purchases or hiking interest rates, the key elements of its dovish monetary policy aimed at helping the economy recover from the pandemic recession. “What (Powell) said seemed to be inline with universal expectations, that he wasn’t going to say much,” said Tom Martin, senior portfolio manager at GLOBALT Investments in Atlanta. “He did confirm that a …