Breadth thrust buy signals? Check. A collapse in volatility? Check.

To many chart readers, it seemed like the latest technical signals were pointing to a fresh and lasting upswing in the stock market — but not so fast.

The S&P 500 is approaching key resistance levels that could unleash a wave of selling and increase volatility in the near term.

Since the benchmark index rallied 14% from tariff-induced lows earlier this month, it is fast approaching its declining 50-day moving average and 200-day moving average.

When the stock market is in a downtrend , as it has been since it made a series of lower highs and lower lows in March and April, the declining moving averages typically represent a level where sellers can overwhelm buyers, driving stock prices lower and extending the downtrend.

"We favor the 200-day average as a gauge of the market's primary trend," Ari Wald, head of technical analysis at Oppenheimer & Co., told Business Insider on Tuesday. "It often serves as support in uptrends and resistance in downtrends."

As of Tuesday afternoon, the 50-day moving average of 5,613 represents 1.2% upside from current levels, while the 200-day moving average of 5,746 represents 3.6% upside.

But from there, it will likely be a tougher hill to climb for the stock market.

"The key question we're focused on is whether the first-quarter weakness was simply a sharp correction within an ongoing bull cycle, or the start of a more extended consolidation following a meaningful trend break," Wald said.

"We lean toward the latter view, and believe the risk/reward profile becomes less attractive as the S&P 500 approaches its 200-day moving average," He added.

Whats more, the S&P 500's 200-day moving average is around the same level where the market peaked in late March, representing yet another reason why selling could take place around 5,750.

"The S&P 500 is reaching a 'confluence of resistance' formed by the 200-day moving average as well as the late March swing low around 5750," David Keller, chief strategist at Sierra Alpha Research, told BI.

"Given the severity of the upswing, we would expect at least a tactical pullback from this resistance zone as the market digests recent gains," he said.