It certainly looked like a breakout, at least for today, but it would have been more convincing if the volumes had not remained thin. As such it looked like a short squeeze engineered by the wiseguys ahead of the FOMC meeting.
SP 500
NDX
"If at the start this cancerous growth in the nation was not particularly noticeable, it was only because there were still enough forces at work that operated for the good, so that it was kept under control. As it grew larger, however, and finally in an ultimate spurt of growth attained ruling power, the tumor broke open, as it were, and infected the whole body." The White Rose, Munich 1942