By Scott DiSavino

Sept 9 (Reuters) -U.S. natural gas futures slid about 3% on Monday on expectations a storm forecast to hit Louisiana later this week will cut demand by causing power outages and reducing the amount of gas flowing to liquefied natural gas (LNG) export plants.

That price decline came despite forecast for more demand next week than previously expected and higher LNG feedgas so far this month.

Another factor that has weighed on gas prices for much of this year was the tremendous oversupply of gas left in storage after a mild winter.

There was still about 10% more gas in storage than normal for this time of year even though injections have been smaller than usual in 16 of the last 17 weeks. EIA/GAS NGAS/POLL

Analysts said those small weekly builds happened mostly because several producers cut output this year after spot prices at the U.S. Henry Hub benchmark NG-W-HH-SNL fell to a 25-year low in the spring and have remained relatively low since.

Front-month gas futures NGc1 for October delivery on the New York Mercantile Exchange fell 6.3 cents, or 2.8%, to $2.212 per million British thermal units (mmBtu) at 9:29 a.m. EDT (1329 GMT).

On Friday, the contract closed at its highest level since July 12 for a second day in a row.

In the Atlantic Basin, the U.S. National Hurricane Center (NHC) projected a demand destroying hurricane will form in the Gulf of Mexico on Wednesday before hitting Louisiana, home to three of the nation's seven big LNG export plants.

Since over 75% of U.S. gas production comes from big inland shale basins like Appalachia in Pennsylvania, West Virginia and Ohio and the Permian in West Texas and eastern New Mexico, analysts said hurricanes were more likely to reduce prices by cutting demand through power outages and knocking LNG export plants out of service.

Twenty years ago, when 20% of nation's gas came from the federal offshore Gulf of Mexico, hurricanes could boost prices by threatening supplies. But, now that offshore region produces just about 2% of the country's gas.

SUPPLY AND DEMAND

Financial firm LSEG said gas output in the Lower 48 U.S. states slid to an average of 102.4 billion cubic feet per day (bcfd) so far in September, down from 103.2 bcfd in August.

Meteorologists forecast weather across the U.S. would remain mostly near normal through Sept. 12 before turning warmer than usual from Sept. 13-24. Energy traders, however, noted that warm weather in mid-September would only average around 75 degrees Fahrenheit (23.9 degrees Celsius), compared with a daily average of 79 F in mid-August.

LSEG forecast average gas demand in the Lower 48, including exports, will rise from 100.7 bcfd this week to 101.2 bcfd next week. The forecasts for next week was higher than LSEG's outlook on Friday.

Gas flows to the seven big U.S. LNG export plants rose to an average of 13.4 bcfd so far in September, up from 12.9 bcfd in August. That compares with a monthly record high of 14.7 bcfd in December 2023.

On a daily basis, LNG feedgas hit a three-month high of 13.6 bcfd on Sunday.

Looking ahead, Berkshire Hathaway Energy's 0.8-bcfd Cove Point LNG export plant in Maryland will likely be shut for about three weeks of routine annual maintenance around Sept. 20, according to the plant's history and notices to customers.

Reporting by Scott DiSavino

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