Mark Hulbert says the market could be in for an “explosive” jump higher, if and when it passes its April highs.

In his latest MarketWatch column, Hulbert says that while the market is trading at almost the same level it was back in late April, “there are a lot of things different about today’s market” versus the late-April market. One big difference: sentiment levels. He gauges sentiment by looking at a subset of short-term market-timers he tracks at his Hulbert Financial Digest. Currently, that group has an average recommended equity exposure of just 25.9%, down from 65.5% when the market was peaking on April 26.

“In other words, the average stock market timer today is less than half as bullish as he was in late April,” Hulbert says. “Since the usual pattern is for advisers to become more bullish as the market rises, and more bearish as it declines, the current low level is quite surprising — and bullish.” With the average short-term timer having three-quarters of their stock portfolio in cash, there’s a lot of dry powder waiting on the sidelines “that could propel the market higher, should these timers decide to once again turn bullish. They are likely to do so in droves if and when the market surpasses its April high. Don’t be surprised if the market thereafter turns in a few explosive days on the upside.”