Today's bar was a bullish bar and went above the high of yesterday's low volume bar. April 27 and April 28 were low volume days as well.
When price continues to put in new highs despite these low volume days it is a good indication price is headed higher. 4250 and 4300 are the next targets for the S&P.
I do not advocate buying into the highs so entering on pullbacks waiting for a price action entry is best.