After the decline to the August 24 low of 1823, the E-mini S&P 500 futures (December) have been moving in a large triangle. The high of the ascending triangle was 1983.75. This was slightly eclipsed on September 16 as the price reached a high of 1989. The breakout wasn't given much credibility though because volatility was expected on September 17 --the day the US decides if it will hike interest rates.
Traders and analysts are torn on whether there will be a rate hike, or whether rates will stay at 0.25%. A lot of volatility was expected, with the result of the decision ultimately deciding the breakout direction of the triangle.
December S&P 500 E-mini Futures (ES), Daily Chart
The Fed left rates unchanged at 0.25% and the market is up incrementally on the news. If the S&P 500 can close on September 17 above the 1983.75 level it indicates a breakout and that price could likely head higher over the next couple weeks. The next resistance area is 2060 to 2080--an area that will likely present a shorting opportunity as the August decline changed the outlook to bearish. A rally right through this resistance area, and above 2100, indicates this August drop was a bear trap and that the long-term uptrend may resume after all.
On the other hand, if the price closes inside the triangle--above 1950 and below 1983.75--the triangle continues. The new upside breakout level would be high seen on September 17 (currently 2000).
A downside breakout of the triangle isn't an immediate threat, but occurs if the price falls below the steeply angled upward triangle currently intersecting at 1950. A decline below that could signal a drop back toward the low of 1823. Before that can occur there are multiple small support levels which have developed near 1920 and 1910 and 1890.
As of 2:15 EST on September 17 the S&P 500 E-mini December contract is trading at 1990, currently signaling the upside breakout.