Investors are bracing for Jerome H. Powell, the Federal Reserve chair, to deliver a stern warning that the bank is far from finished in its campaign to slow inflation with higher interest rates.On Friday, Mr. Powell will speak at the Kansas City Fed’s Economic Policy Symposium in the Jackson Hole resort area of Wyoming, the central bank’s most prominent annual conference. Other Fed officials have recently tried to send the message that even after data on consumer prices showed that inflation eased up in July, the central bank is intent on damping demand by raising borrowing costs, which is normally a bad thing for the stock market.But for most of the past two months, stocks have rallied. From mid-June to mid-A …
