One of the broadest measures of the U.S. stock market, the Wilshire 5000, is drooping this month, feeding speculation that market momentum has shifted to the downside after a relentless move up in 2013, according to USA Today.

Wilshire Associates said the Wilshire 5000 has fallen 10 days so far in August, similar to May 2013, when stocks took an extended tour downward before recovering.

"Bullish investors may be able to dismiss the market's skid, but not if it continues much longer and not if August gets uglier," USA Today predicted.

Editor’s Note: Dow Predicted Will Hit 60,000 — Buy These 4 Stocks Now(Shocking)

The month of August ushers in the month of September, which is traditionally the weakest month of the year for U.S. stocks by modern historical measures.

The newspaper noted investors need to monitor when the Federal Reserve begins to taper off its $85 monthly bond-buying program, which could spark an increase in interest rates and curb housing activity.

The Wilshire 5000 Index tracks the market value of all stocks actively traded in the United States. It is intended to measure the performance of most publicly traded companies headquartered in the United States.

Ralph Acampora of the New York Institute of Finance, a veteran stock market technical analyst, suggested on Twitter that a stock market resurgence in the short term may not last.

Acampora, a proponent of the Dow Theory to predict stock moves, said that from its Aug. 2 intra-day high to Wednesday's intra-day low, the Dow Jones Industrial Average lost 777.59 points, or 4.9 percent.

"It's oversold — due for a minor rally," he tweeted.

"Use any counter-trend rally(s) to continue lightening-up positions. Don't use the cash to buy until we see the final end to this decline," Acampora advised.

Martin Leclerc, chief investment officer at Barrack Yard Advisors, told The Wall Street Journal that Fed intentions and rising yields "will likely dominate the narrative" in the near term.

"The Fed is not really changing its tune," Leclerc said. "We've been in the cautious camp, particularly with respect to U.S. equities, and what we've seen lately hasn't changed that."

Editor’s Note: Dow Predicted Will Hit 60,000 — Buy These 4 Stocks Now(Shocking)