It was a strong open with the NYAD above 3, which almost always ends with a green day. That's what happened today but the last 2 hours saw increasing volume and the last hour saw a solid sell off. The NYAD was also downslope for the last 2 hours with a big volume drop in the last 10 minutes.
The SPY TrendX indicates some upside potential but we're clearly hitting strong resistance at this point and although Thursday's odds are neutral Friday is options expiration and the odds for a downturn then increase significantly.