The horizontal lines on this SPY chart mark all FOMC meeting announcement days in since the beginning of 2014. Other than one exception following the December 17th, 2014 FOMC announcement*, the stock market traded lower within a few days to a couple of weeks.
*The rally that followed the December 17th FOMC announcement came on the heels of a 7 session, 5%+ correction in the SPY. Additionally, following the oversold/FOMC induced rally which peaked 7 days later, the SPY fell back sharply to the Dec 17th announcement level within just 5 sessions, quickly erasing that entire post-Fed rally.
Bottom line: While the primary trend in the market has been bullish in recent years, in nearly all instances, any post-FOMC announcement rallies were faded within hours or days. Taken in light with the current bearish technical posture of the equity markets, I would put good odds that the market will be trading lower within the next week or so.