Why the bull market could end tomorrow

March 21, 2014, 2:00 PM UTC

FORTUNE — Timing the market, to many investors, is a science akin to fortune-telling or tarot cards. Financial experts warn retail shareholders constantly: Don’t try this at home. Yet with the market going on a sixth year of gains and hovering near record-high levels, the bull seems more vulnerable every day. (For more on those concerns, see “Five reasons the market must fall” in the April 7, 2014 issue of Fortune.)

Investors from the fundamentalists to the quants to the technical analysts have offered their readings of the tea leaves, circulating charts pointing to the “death cross,” 1929 market parallels and other red flags that signal a market retreat. Still, few dare to make predictions about if, when, why or how much the market will drop. After all, in the last few months, each supposed market top has turned out to be just another rest stop on the climb up, leaving the bears sounding like whiny backseat drivers: “Are we there yet?”

Tom DeMark is an exception. The market timing precisionist who famously called the S&P 500’s 2011 bottom within a point or so, months before it happened, told Fortune this week that the bull had just a few days left to live. “We’re about to become bearish,” predicts DeMark, CEO of DeMark Analytics, which provides market indicator tools to traders and investors.

He didn’t stop there. Analyzing the course of the S&P, he circled a specific point at which he expects the market to pivot: 1,931 on the index. “Its pretty clear that this next rally, the one we’re currently in, will be a good top,” DeMark says. “And it looks like it’s going to be a pretty important top that should last at least three months.” During that time, brace for a decline of at least 11%, he adds.

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Before that happens, though, the S&P 500 must break its March 7 record of 1,878 (DeMark is eyeing 1,882)  — and then break it again: “The gyrations here are setting up for one final burst,” he says.It may be another week yet.”

Even if you’ve never heard of DeMark, you might still be familiar with his work — in particular, a chart overlaying the Dow Jones Industrial Average in 2013 with stock movements in 1928 and 1929, showing an uncanny similarity to market performance just before the historic crash that led to the Great Depression.

“That was more for entertainment,” says DeMark, who has tried to play down the significance of the chart since it went viral back in the fall, and continues to be referenced in notes by traders and analysts. (The pattern, however, diverged in January, DeMark adds.)

To be sure, the “top” DeMark foresees now may just portend a bigger breather than stocks have had for the last few years, before the bull comes roaring back. And there’s reason to be skeptical that the market will correct at all in the near future, as one man’s pessimism is another man’s bull case. Many investors are still squinting at the almost 6% emerging markets-driven drop in late January, wondering if it even qualifies as a correction.

“This bull market remains unloved, in our opinion,” Sam Stovall, chief equity strategist for S&P Capital IQ, wrote in a recent note to clients. “Anecdotal samplings of audience opinions still point to an overwhelming number of investors who are awaiting “the big one.’” That makes Stovall all the more bullish: He expects the S&P 500 to fly as high as 2,030. The index would have to slide pretty far downhill, to lower than 1,627, before he’d consider that the bull had come home from pasture. Until then, he says, every correction is a buying opportunity.

DeMark, for his part, admits he’s been wrong before, but grants the current bull market two weeks at best before it begins to recede. “Usually I know right before it happens,” he says.

Whatever comes to pass, however, most investors won’t see it coming. The best strategy? Ride the market out as long as you can, because the bull inevitably comes back, eventually.