Both S&P and DJIA as depicted in the charts have made 3 waves down from recent highs. If the lows are broken, both indices will most probably decline towards 12800(DJIA) and 1380(S&P).
This could just be wave A. The upward move could be wave B and we now are expecting wave C that could coincide with the Jackson Hole speech of Bernanke.
Therefore 1398 (S&P) and 13027 (DJIA) are important supports that could work as a stop-reverse. In the case that the 3 wave correction has ended at the above mentioned support levels, a new upward move is ready to start and Friday's speech at Jackson Hole could be the reason for the markets to rally.
If however the markets slide sideways close to the resistance levels (13176 DJIA-1416 S&P) one could try and sell short with those levels as a stop reverse.
GDP figures are being announced before open and could provide volatility in the futures market. Taking action before the announcement should be protected with stop loss orders.
Thank you for taking the time to read my thoughts.