Update (5:15pm): The S&P closed well below 5,255, and even spoos failed to ramp above the closely watched CTA trigger level in a last minute buying frenzy despite the $6 billion Market on Close sell imbalance (an indicator of CTA liquidation pressure).
Which means that what happens next is in the hands of Japan (and specifically the clueless Bank of Japan): another painful carry trade unwind here and tomorrow will be ugly. On the other hand, should USDJPY ramp and pull Japanese stocks higher with it, and the trans-Pacific selling may finally see some respite.