Today, the major indices gapped down at the open and closed near their lows. Here's how the S&P 500 Index (SPX) closed, with the VIX overlayed (daily chart).
This monthly chart of the SPX:VIX ratio shows today's close below major support of 200.
The momentum indicator has fallen to just above the zero level on this timeframe...a drop and hold below would indicate increased selling pressure in equities.
P.S. Throw a little news into the mix regarding volatility...
...plus the fact that the U.S. was not the only world market to be hit in today's large-scale sell-off...and we'll likely witness some interesting action tomorrow, world-wide.