US natural gas prices fell more than 1% Friday to $2.85 per MMBtu (million British thermal units, a gas energy measure), erasing the previous session's gains as weather forecasts turned cooler. Above-average temperatures are expected to cover a smaller area of the South and Southeast from September 22 to October 1, potentially reducing gas demand from power generators used for air conditioning. Prices had risen Thursday after the EIA (U.S. energy statistics agency) reported a below-average storage build for the week ended September 11. The increase narrowed the inventory surplus over the five-year average to 118 Bcf from 148 Bcf a week earlier, as late-season heat lifted power-sector demand. Strong production continued to pressure prices, with Lower 48 output averaging 113.1 bcfd in September, above August's record monthly average of 112.2 bcfd. Meanwhile, average flows to the nine major US LNG (liquefied natural gas) export facilities were expected to decline to a three-week low of 17.5 bcfd, mainly because of maintenance at Cameron LNG in Louisiana.