As indicated on the chart, today's drop may start a significant decline. But the market does not follow a script. Stocks can and will do anything. As traders, we can only evaluate the potential rewards against the risks of trading a set-up.
Let's look at SPY:
SPY also possibly completed a bearish pattern today: a 3-month Head and Shoulders top. It now rests on its 200-day simple moving average.
Finally, let's look at a 1-year chart of the NYSE index:
What seemed like attempts to break out (up) of a 9-month continuation H&S bottom has now turned into something else. Yes, stocks can still go up from here, but let's consider another possibility. The next chart focuses on the last 6 months:
We see a possible bearish broadening top (megaphone) and today's decline may have completed the pattern. But remember that classical charting is about possibilities and never predictions or guarantees. Stocks may recover quickly from today's decline and invalidate this broadening top interpretation. Keep an open mind.