(Bloomberg) -- Boston is in line for as much as 18 inches (46 centimeters) of snow on Sunday and Monday from a storm coming on top of near-zero temperatures that have prompted city officials to declare a cold emergency.The National Weather Service’s forecast calls for 12 to 18 inches of snow across much of southern New England, including the Boston area, with the first flakes falling in the late morning or early afternoon on Sunday. That stands to be the most snow Boston’s received from a single storm in fo ...