It's amazing that whenever a flash crash occurs it doesn't disturb the waves, and even conforms to trend lines as seen by this chart from @BlackBetty
There will be many more flash crashes, and they're why options should be a major part of every trader's bag of tricks. For more: check out this great post by my friend Sean McLaughlin: Living In A High Frequency World
With yesterday's reasonably strong close, the pressure remains on the upside. The teeny gap at 1588.85 could well be the target. At this point, considering the close above 1575, so could a new high.
Yesterday's 1563.03 low is the key to lower prices, and unless it breaks in the next two or three days, the buy pressure remains. Volume or no volume.