Louise Yamada has a message for investors: sell now.

On CNBC's "Futures Now" Tuesday, the veteran technician called this week's rally leading into the Federal Reserve's big announcement nothing but a mirage, and she warned against the disturbing price action "beneath the surface" of the broader market.

All major U.S. indexes jumped Tuesday, with the seeing its first two-day winning streak since early November in anticipation of what could be the first interest rate hike in nearly a decade. The move higher comes at a time of whipsaw action for stocks, with the S&P 500 coming off its worst week since mid-August.

"I think [the volatility] will certainly continue," said Yamada. "With all of these rallies you still have only 25 percent of NYSE stocks in the New York Stock Exchange above their 200-day moving average," she said. "It's worthy of being extremely cautious."

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According to Yamada, investors must ask themselves four key questions when looking at this market: Does the advance have something to reverse? Has the uptrend been violated? Has support been violated? And, has a downtrend initiated?

"With every answer that comes out yes we would suggest people take money off the table," said the founder of Yamada Technical Research Advisors. Yamada added that with the market now in a downtrend, "one should be out of the market."

Looking at a chart of the New York Stock Exchange composite — which is composed of a basket of more than 1,500 stocks — Yamada noted that the index has been forming a topping process for the last two years.

Furthermore, she said a downtrend has been in place since its July peak and the index has recently formed a monthly death cross. "The recent rally in November failed under that downtrend and broke under that 10,050 support, which now represents resistance," she said.

For Yamada, all of these negative indicators point to a retest of the August low, which is nearly 10 percent down from where the S&P 500 is currently trading. "I think that we're probably looking at a cyclical bear market until proven otherwise," she said.