BUZZ-US natgas firms fall on warmer weather forecasts

** Shares of U.S. natural gas companies fall as natgas futures at a three-week low NGA/

** U.S. natgas futures NGc1 down 3.9% at $3.55 per million British thermal units (mmBtu), on forecasts for warmer weather and lower heating demand over the next two weeks

** NextDecade NEXT.O falls 2.9%, New Fortress Energy NFE.O falls 1.1% and CNX Resources CNX.N falls 1%

** United States Natural Gas Fund UNG.P ETF down 3.2% and ProShares Ultra Bloomberg Natural Gas BOIL.P ETF down 6.3%