** Shares of U.S. natural gas companies rise, tracking an increase in natgas futures NGA

** U.S. natgas futures NGc1 up 1.5% at $3.286 per million British thermal units

** Prices rise driven by a small decline in output, along with increases in gas flows to liquefied natural gas $(LNG)$ export plants and forecasts for more demand this week than previously expected

** Natgas companies: CNX Resources CNX.N up 2.4%; Williams Companies WMB.N up ~3%

** Natgas ETFs: United States Natural Gas Fund UNG.P rises 2%; ProShares Ultra Bloomberg Natural Gas BOIL.P advances 5%

(Reporting by Dharna Bafna)

((Dharna.bafna@thomsonreuters.com))