JPMorgan Chase (JPM) - Get Report chief economist Anthony Chan expects Federal Reserve Chair Janet Yellen to strike a flexible tone in terms of the timing of the next interest rate hike in her Jackson Hole, Wyo. speech on Friday. 'The Federal Reserve does want to raise rates this year,' he said. 'One of the most important things for the Fed right now is to make sure the financial markets are prepared for a rate hike.' Chan said the markets are pricing in a 57 percent chance of a December rate hike, but the Fed would like those odds to increase. TheStreet's Scott Gamm reports from Wall Street.