Natural-gas prices closed barely higher Tuesday, with traders continuing their tenuous push as forecasts show a heat wave on the way. The front-month September contract settled up 0.9 cent, or 0.2%, at $3.974 a million British thermal units on the New York Mercantile Exchange. It narrowly advanced a three-week high set Monday and was the market’s sixth gain in seven sessions. Only two of those gains have been larger than 1%. Several forecasts grew notably warmer Tuesday, causing the early buying, analysts said. Heat causes people to turn on air conditioning and use more gas-fired electricity, and the pattern developing for the weekend includes some of the strongest heat in what has been a mild season. Above-normal temperatures should cover nearly all of the country by Monday, according to MDA Weather Services. The record pace of production had dropped gas prices about […]