Heading into August, the S&P 500 had traded in a tight range between 2,050 and 2,125 over the prior six months.  After completely breaking down below that range, the index has formed a very clear “flag” pattern.  Check it out in the chart of the S&P below.  These flag patterns often result in a big move in either direction, and as you can see below, we’re at the end of the flag right now heading into the FOMC announcement on Thursday.