Gap trap
Futures are gyrating around a 1% loss for the S&P 500 at the open. Using SPY, that's the 2nd-largest gap down in 3 months. Below, we can see SPY's returns from the open of any day it gapped down at least 1% within 2 days of having set a 52-week high.

It had a mild tendency to rally intraday, but then showed mostly weakness in the days, even weeks, following.
