** Shares of U.S. natural gas companies up, tracking a rise in natgas futures NGA/
** U.S. natural gas futures NGc1 up 4.3% at $3.49 per million British thermal units
** Natural gas prices rise on a decline in output and forecasts for cooler weather and more heating demand this week than previously expected
** Natgas companies: Cheniere Energy LNG.N up 1.6% and Expand Energy EXE.O climbs 1.8%
** Natgas ETFs: United States Natural Gas Fund UNG.P up 3.24%, while ProShares Ultra Bloomberg Natural Gas BOIL.P climbs 4.26%
(Reporting by Varun Sahay in Bengaluru)
((Varun.sahay@thomsonreuters.com))