Currently there is some divergence between the ROC and the price of SPY. ROC (rate of change) is a momentum indicator.
There have been multiple divergences like this before, and each one resulted in a trend reversal.
The ROC has moved back towards the mid-line, which is a sign of waning momentum. If we cross below the mid-line (0 value) then we could see some downward momentum and lots of selling.
We also just hit the 21-period moving average in the previous session. If we cannot stay above it then I will remain bearish.