Here is a five minute bar chart showing today's e-mini day session. Volume has been generally low all day. This lack of activity has prevented the market from reaching either of the range estimate limits I expected for today (blue rectangle). Dullness at the top of a rally like this usually means that the market is about to begin a substantial reaction. There are two midpoint support levels to watch in this regard. The midpoint of the day session range (dashed red line) and the midpoint of the first hour reaction (dotted purple line). A drop from the 829 high that is as big as today's early reaction would put the market at 817 (purple rectangles).
I suspect that the market is about to break these support levels because it has been rallying on reduced volume all day. If it does break them I think a 40-50 point drop from the high will then develop. This would bring the e-minis down to the midpoint support at 781.