The last time the market was moving off a similar overbought condition was January 7th and that day’s bar was very similar to similar to Thursday’s. It included an unfilled gap down from an overbought condition and a selloff of close to 3%. Below is a study that appeared in the January 8th Subscriber Letter that looked at similar situations. Note the study does not include the January 7th instance which led to further selling.
I also found when doing this study that the stronger selloffs led to stronger further declines on average.