The recent rally in the U.S. stock market could be even stronger than it look, reports an article in MarketWatch. Though the S&P 500 is up 6.6%, the Nasdaq Composite and the Russell 2000 are up 8% and 9.9% respectively from their May lows, those numbers could signal a deeper strength given that, before the Memorial Day weekend, stocks whose prices dropped did so with less volume than the stocks that went up in price.

That could be a sign of what’s known as market “thrust,” according to Hayes Martin, president of the advisory firm Market Extremes. Martin told MarketWatch that thrust seen before the holiday weekend “signifies a level of intense buying pressure that is rarely seen…comparable to extremes at a number of significant lows.” On previous occasions where thrust has been this strong, the market rebounded with healthy average returns.

Martin’s track record of predictions is very good; when MarketWatch last caught up with him earlier in May, he foresaw an 8% to 15% market rally—a prediction that came true. With the strength of that prediction, Martin has turned a bit more bullish, and now believes the market will rally 15% to 25% from its recent low, saying that the biggest gains will be in the Nasdaq and tech sectors.

But he’s not sure we’re out of bear market territory yet, he tells MarketWatch, though he doesn’t think it’s likely that the recent lows will be retested in the next month or so. And the lackluster performance the day after Memorial Day hasn’t changed his mind on the market’s potential for future gains. The aftermath of the market thrust, he says, will span over several months, not just one trading session.