Fed Chairman Ben Bernanke during his Senate testimony Tuesday.

Investors in U.S. bank stocks may be in for a volatile ride over the next two weeks as the Federal Reserve releases results of its annual stress tests of bank capital in two steps.

Late on Thursday, the agency is expected to reveal how much capital 18 large banks would maintain under a hypothetical severe economic downturn. A week later, the Fed plans to disclose how the banks would have fared if they had first spent some of their capital buying back shares or paying higher dividends.