If you're trying to guess when this market might reverse, the most important fact to keep in mind is that there has been only one weak afternoon so far in 2017. The market has consistently gained strength during the day and closed strong. Until that changes, you are wasting your time trying to call a market top.
There is an old saying that "dumb" money tends to trade the open and "smart" money trades the close. That is a questionable proposition, but there probably was some truth to it many years ago when institutional buyers had to deal with liquidity issues and didn't cross trades till later in the day.
Whether the buyers are dumb or smart isn't the issue now, but when there is a willingness to buy stock to hold overnight then there is very likely to be positive momentum. Buying late in the day is a product of positive sentiment and feeds on itself.
If you want to try to call a market top, then keep a close eye on this pattern. We had a good example Thursday after the market had blasted higher following the Trump congressional speech; however, the market regained its footing on Friday and is showing signs of afternoon improvement again today.
This morning, breadth was running 3-to-1 negative and hasn't improved much, but the big-caps have found some bids and that is driving the index bounce. We still have a couple of hours to go and if this bounce fizzles out before the close it will be notable.
Detecting a change in market character will give you a trading advantage and right now the most important characteristic of this market is afternoon strength. When that shifts, we should be ready to shift as well.