Short-term strength is often followed by short-term weakness, but when that short-term strength is unusually impressive, it can create a situation where that extreme strength will beget more strength. When the market leaves an unfilled up gap that is considered a sign of strength. When it does it 2 days in a row and closes at a 50-day high, that can be considered exceptional strength. That is what happened on Friday, and past performance is shown in the study below.
The size of the follow-through isn't terribly large. But it has been very, very consistent that at least some follow through was achieved in the next few days.