U.S. stocks have some powerful negatives tugging at them, not the least of which are the Shanghai "panda bear" market and a global commodities rout.

But there is also the Fed, and it meets Tuesday and Wednesday amid shaky markets. While the U.S. central bank is not expected to take any action or make any major new comments, some traders expect its statement to sound hawkish to a nervous market as the Fed moves toward its first rate hike in nine years. Positive tones on the U.S. economy from the Fed could be a positive for stocks, even though it could signal a rate hike ahead.