By Rahul Paswan

Sept 20 (Reuters) -U.S. natural gas futures slipped more than 1% on Friday, weighed down by lower demand forecasts for next week and oversupply of fuel left in storage.

Front-month gas futures NGc1 for October delivery on the New York Mercantile Exchange fell 1.9 cents or 0.8% to $2.33 per million British thermal units (mmBtu) by 09:58 a.m. EDT (1358 GMT), after rising to its highest since Sept. 16 at $2.38 per mmBtu, earlier in the session.

However, the contract gained about 0.8% so far this week, heading for its fourth straight weekly gain.

"Power burns have also been strengthening over the last few days which again is another factor that's certainly helping demand, but that's somewhat offsetting slightly weaker LNG and I think that there's a lot of moving pieces today and the market is pretty much undecided as to where to go in the near term, said Robert DiDona of Energy Ventures Analysis.

Financial firm LSEG estimated 122 cooling degree days (CDDs) over the next two weeks, lower than 124 CDDs forecasted on Thursday. The normal for this time of year is 86 CDDs. Cooling degree days, used to estimate demand to cool homes and businesses, measure the number of degrees a day's average temperature is above 65 degrees Fahrenheit (18 degrees Celsius).

LSEG forecast average gas demand in the Lower 48, including exports, at 99.6 billion cubic feet (bcfd) per day this week to 98.7 bcfd next week.

LSEG forecast average gas supply in the Lower 48, including exports, at 101.8 bcfd this week to go up to 101.9 bcfd next week.

LSEG said gas output in the Lower 48 U.S. states slid to an average of 102.0 bcfd so far in September, down from 103.2 bcfd in August.

On Thursday, the U.S. Energy Information Administration (EIA) said utilities added 58 billion cubic feet (bcf) of gas into storage during the week ended Sept. 13, which was still about 8% more gas in storage than normal for this time of year. EIA/GASNGAS/POLL

"I think prices even through November are going to remain relatively favorable for gas fire generation and that's going to be an added feather to the cap for demand, not just a seasonal increase of colder weather giving a lift to residential and commercial load, but also the fact that power burns could remain strong in the very near term," DiDona said.

Gas prices were trading around $11 per mmBtu at the Dutch Title Transfer Facility (TTF) benchmark in Europe TRNLTTFMc1 and $13 at the Japan Korea Marker (JKM) benchmark in Asia JKMc1. NG/EU

In other news, Chevron CVX.N does not want to invest in the construction of U.S. LNG plants, as it is not the best use of the company's capital and it can easily sell its U.S. gas, said a top official on Thursday. The head of Chevron's midstream, Colin Parfitt, also ruled out taking an equity stake in Woodside Energy's WDS.AX impending purchase of Louisiana-based Driftwood LNG.

Meanwhile natural gas production has begun earlier than planned at Argentina's Fenix offshore field, French oil major TotalEnergies said on Friday. The $700 million project, initially scheduled to begin operating in November, has a production capacity of 10 million cubic meters of natural gas per day, representing 8% of Argentina's total production and about 7% of annual consumption.

Reporting by Rahul Paswan in Bengaluru; Editing by Nick Zieminski

For gas data on the LSEG terminal type ENERGY in the search bar and then go to the GAS drop down and the NORTH AMERICA drop down.

For Interactive Map, type 'Interactive Map' in the box at upper left of the LSEG terminal

For graphics on Baker Hughes rig counts, see: http://graphics.thomsonreuters.com/15/rigcount/index.html

For next-day SNL U.S. gas prices, see: 0#SNL-NG

For next-day SNL U.S. power prices, see: 0#SNL-PWR

For U.S. natgas price and storage polls, see: NGAS/POLL

For U.S. nuclear power outages, see: NUKE/

For U.S. Northwest hydro power report, see: NWRFC

For U.S./Canada natural gas rig count vs Henry Hub futures price, see: http://tmsnrt.rs/2eT9k44

For the U.S. natural gas speed guide, see: USGAS

For the U.S. power speed guide, see: USPOWER

To determine CFTC managed money net position add (NYMEX Henry Hub options and futures combined 3023651MNET) plus (ICE Henry Hub options and futures combined 3023391MNET divided by four) plus (NYMEX Henry Hub swaps options and futures combined 303565BMNET divided by four) plus (NYMEX Henry Hub penultimate gas swaps 303565CMNET divided by four)

NYMEX Henry Hub options and futures combined 0#3CFTC023651

NYMEX Henry Hub futures only 0#1CFTC023651

ICE Henry Hub options and futures combined 0#3CFTC023391

NYMEX Henry Hub swaps options and futures combined 0#3CFTC03565B

NYMEX Henry Hub Penultimate gas swaps 0#3CFTC03565C