Momentum a Powerful Ally for Stocks as Whiplash Rally Rolls On

There are many reasons to doubt the rebound in US stocks, but it has at least one powerful factor on its side: momentum.

History shows that the rally may extend further than investors might expect and bode well for stock performance down the road. Though it’s not infallible, that trend is good news for traders betting that stocks might have more room to run following a dismal start to the year.

The bounce in the S&P 500 Index has already been one for the record books. The benchmark index notched its ninth-straight daily gain on Friday, the longest stretch ...