NEW YORK ( TheStreet) -- U.S. stock futures suggested Wall Street will open slightly higher Tuesday as investors turn their attention to a speech later this week from Federal Reserve Chairman Ben Bernanke. European stocks were trading lower, while Asian shares finished mixed. Japan's Nikkei 225 index lost 0.6% to close at 9,003.29. Speculation is that Bernanke, in his speech Friday in Jackson Hole, Wyo., will use his speech to call for more for more bond purchases. European Central Bank President Mario Draghi won't be attending the Jackson Hole summit because of the "heavy workload foreseen in the next few days," a spokesman said. The economic calendar in the U.S. Tuesday includes the S&P/Case-Shiller home price index for June at 9 a.m. EDT and consumer confidence for August at 10 a.m. U.S. stocks on Monday finished mixed on thin volumes Monday as traders looked ahead to the Jackson Hole summit. The Dow Jones Industrial Average lost more than 33 points, or 0.25%, to close at 13,125. The S&P 500 dipped less than a point, or 0.05%, to settle at 1410.44, while the Nasdaq rose more than 3 points, or 0.11%, to finish at 3073. Tropical Storm Isaac was on the verge of becoming a full-blown hurricane Tuesday as it rolled over the Gulf of Mexico toward Louisiana. Forecasters predicted the tropical storm would power up to hurricane strength later in the day and be at least a Category 1 hurricane by the time it's expected to reach the coast of southeast Louisiana early Wednesday. The forecast track has the storm aimed at New Orleans, but hurricane warnings extended across 280 miles, The Associated Press reported. The majority of oil production in the Gulf of Mexico has been halted in preparation for the hurricane. Apple ( AAPL) on Monday promoted Dan Riccio and Craig Federighi to senior vice presidents and said Bob Mansfield, who was going to retire, will stay with the company to work on future projects. Mansfield is senior vice president of hardware engineering at Apple, reporting to CEO Tim Cook.