A closely watched gauge of the U.S. economic outlook rose in April, indicating the economy will strengthen after a severe winter caused a slowdown, a private research organization reported Thursday. The Conference board said its index of leading economic indicators—designed to forecast U.S. economic activity in the coming three to six months—rose 0.4 percent in April following a 1 percent gain the previous month. The strength in April was led by improving housing and financial-market conditions. The gains in April and March indicate the first-quarter slowdown was more the result of harsh weather than underlying weakness. Conference Board economist Ken Goldstein said stronger spending by consumers and higher business investment should support growth in coming months.