I don’t like the trick below, because whenever this happens it actually means the market is in an uptrend therefore shorting based on the trick is not pleasant at least for a few days.
Tomorrow is NFP day which usually reverses whatever happens in the morning: gap up then probably close < open while gap down then close > open. Although I believe the job data won’t be bad but the market has been opened with a gap up for 4 days in a row, so I don’t know if it could gap up again tomorrow morning and still that gap up, if any, would be the SPY’s 15th unfilled gaps.