I thought this was an interesting chart pattern for the SPY. Note the gaps for the last three days (June 18, 19, and 20). Futures as of 1 am on the 21st indicate another gap, but this time up. We'll see what happens.
If it gaps up, and the gap doesn't close in the first 30 minutes, I might place a long trade.
Lower lows, without higher highs, signal weakness. Tread with caution. Remember your stops. Calculate your positions size based on calculated losses first.