Those low gas prices on station signs aren’t going away soon, the government says. In a dramatic shift from previous forecasts, the Energy Department predicted Wednesday that the average price of gasoline in the U.S. will be below $2.94 a gallon in 2015. That a 44-cent drop from an outlook issued just a month ago. If the sharply lower estimate holds true, U.S. consumers will save $61 billion on gas compared with this year. Rising oil production, particularly in the U.S., and weak spots in the global economy have led to a sharp reduction in oil prices over the past...