3pm reversals

Besides the 10:30 reversal period, which I see occuring more on range days, I also notice 3pm as a reversal period on trend days. My hypothesis is that automated trading programs close out positions at this time period when profitable and the price is below or above the VWAP.(many automated systems trade based on VWAP with exit points set at this time period)

What are other reasons for the 3pm reversal? Bonds closing.

Here is a great article from LBR on the subject: LBR article

Here is an example. The catalyst for the breakout was FOMC minutes.