Santoli: Why investors should be on high alert heading into September

Get Mike Santoli's Market Memo in your inbox first. SUBSCRIBE HEREIn markets as in movies, suspense builds through the slow, quiet scenes of the second act.The stock market is doing just enough, through slim trading volumes and narrow index trading ranges, to escape August with its uptrend intact.The S&P 500 is within half a percent of where it closed three weeks ago. It has slouched and equivocated in the two weeks since it hit the last record high just above 7800.But the index has stayed within 2% of the peak, the pullbacks so far halting a handful of points above what had been the top of the former multi-month range.Sure, the upwelling of relief that greeted Nvidia's strong results and bold guidance was dramatic. But for the full week, the stock was up just 1.3%, back to levels from three months earlier.Semiconductors as a group held right where they "should" have, preserving the path of their post-July rebound.The market, in other words, has done its best not to do anything that would require disturbing the portfolio managers at the beach.This is where one is conditioned to expect a discussion of calm before storms, of late-summer hurricanes and the punishing realities of S...