Federal Reserve Chair Janet Yellen could cement the case for a U.S. interest rate hike ahead of the Fed’s Dec. 15-16 policy meeting, with public appearances over the next two days at a high-profile economics group and before a joint committee of Congress. When Yellen takes the stage at the Economic Club of Washington shortly after noon on Wednesday, she will do so with market expectations already aligned behind a December hike, and the flow of economic data since the Fed’s last meeting offering no clear reason to hold back.