A forecast for a coming cold spell prompted a rise in the price of natural gas in the United States on Tuesday as it pointed to stronger demand for the commodity. On Wednesday morning, however, natural gas prices were falling once again as mild weather set in and storage levels remained above the five-year average. There will be some upward pressure on U.S. natural gas prices throughout the month as the cold spell is forecast for the final week of January. Even with a brief rebound, natural gas prices in the United States remain much lower than…