Natural-gas prices closed at a three-week high as weather forecasts show some warmer temperatures on the way. Prices for the front-month September contract settled up 8.6 cents, or 2.2%, to $3.962 a million British thermal units on the New York Mercantile Exchange. It was the highest closing price since July 16, the last time gas prices closed above $4/mmBtu. Gas gained 4.3% on the week, the market’s largest percentage gain since the week ended March 28. It finished higher in four of the past five sessions. Several factors created the perfect conditions for a brief rally Friday, said Anthony Lerner, senior vice president of industrial commodities at brokerage R.J. O’Brien in New York. It started with weather, several analysts said. Though forecasts are mixed, they are showing some spurts of summer heat likely to come in parts of the country both […]