The index last closed below its 50-day moving average on April 10, which marked the end of a correction phase that included a 5,000-point drop at its low point

The Dow's fall below its 50-day moving average could warn that further weakness may be coming.

The recent weakness in the stock market is now more than just routine volatility, as the break of a key support level suggests the declines may have become a trend.

The Dow Jones Industrial Average DJIA closed Tuesday down 0.8% at 52,766.88 - below its 50-day moving average, which stood at 52,849.85, for the first time in nearly five months, according to FactSet data. Additionally, the S&P 500 SPX and Nasdaq Composite COMP both ended the day less than 1% above their respective 50-DMAs.

Many use the 50-DMA to track a stock or index's short-term trend. If a charted instrument falls below that line after an extended period above it, that can be viewed as a warning that the trend may have flipped from rising to falling.

As JonesTrading Chief Market Strategist Mike O'Rourke put it, when widely followed moving averages like the 50-DMA are broken, "you can see short-term movement in the direction of the break, as some technical traders and quantitative trading models" bet on follow-through buying and selling.

There are many factors behind the recent weakness in stocks that has brought the indexes down to their 50-DMAs. Rising tensions in the Middle East have boosted oil prices (CL00) (BRN00), which could add more pain to consumers already hurting from stubborn inflation. And that inflation, coupled with ballooning U.S. government debt, has led to a surge in longer-term Treasury yields, which raises borrowing costs for consumers and companies, and provides an alternative "safe" investment at a time of heightened uncertainty.

"The biggest thing right now is interest rates," Adam Turnquist, chief technical strategist at LPL Financial, told MarketWatch. At a 4.8% yield on the 10-year Treasury note BX:TMUBMUSD10Y, "that, in my mind, means we will retest 5% - and that's problematic for areas like the tech sector."

Until Tuesday, the Dow had closed above its 50-DMA every day since April 11. JonesTrading's O'Rourke noted that the 50-DMA had fended off pullbacks in June and July. The latter was a very close call - the Dow closed less than 2 points above it on July 29 - but all that did was confirm that the 50-DMA was support. On July 30, the Dow started a five-day, 2,291-point, 4.4% rally to close at a record 54,349.12 on Aug. 5.

The last time the Dow closed below its 50-DMA was on April 10. That was a couple weeks after the index had suffered a 5,012.50-point, 10% drop - from its then-record close of 50,188.14 on Feb. 10 to a seven-month low of 45,166.64 on March 27.

Effectively, that correction - which many define as a decline of at least 10% to just shy of 20% - ended with a close above the 50-DMA. From April 10, the Dow rallied 20.3% to its Aug. 5 record close of 54,349.12.

The Dow ended Tuesday just 2.9% below its record close, but also at its lowest level since July 31.

Meanwhile, the S&P 500 fell 0.7% on Tuesday to 7,631.47, which was 0.8% above its 50-DMA of 7,570.61. The Nasdaq Composite ended the day down 1% at 26,099.77, or 0.6% above its 50-DMA of 25,954.52.

-Tomi Kilgore -Joy Wiltermuth