By Scott DiSavino

Oct 31 (Reuters) -U.S. natural gas futures slid about 2% on Thursday on forecasts for mild weather to continue through mid November, keeping heating demand lower than usual for this time of year and allowing utilities to keep adding more gas into storage than normal for a few more weeks.

Analysts forecast U.S. utilities added 82 billion cubic feet (bcf) of gas into storage during the week ended Oct. 25. That compares with an increase of 77 bcf in the same week last year and a five-year (2019-2023) average rise of 67 bcf for this time of year. EIA/GAS NGAS/POLL

If correct, that would be the first time utilities added more gas than usual into storage for two weeks in a row since October 2023. Those injections would boost stockpiles to about 5% above the five-year average.

Prior to last week, storage injections had been smaller than usual for 14 weeks in a row because many producers reduced drilling activities so far this year after average spot monthly prices at the U.S. Henry Hub NG-W-HH-SNL benchmark in Louisiana fell to a 32-year low in March. Prices have remained relatively low since then.

Front-month gas futures NGc1 for December delivery on the New York Mercantile Exchange (NYMEX) fell 6.2 cents, or 2.2%, to $2.783 per million British thermal units (mmBtu) at 9:12 a.m. EDT (1312 GMT). On Wednesday, the contract closed at its highest since Oct. 4.

Open interest in NYMEX futures, meanwhile, rose to 1.670 million contracts on Oct. 29, the most since October 2018.

In the spot market, pipeline constraints caused next-day gas prices at the Waha hub NG-WAH-WTX-SNL in the Permian Shale in West Texas to fall into negative territory for a record 41st time this year.

Even though prices have turned negative five times so far in October, analysts have said they expect them to remain in positive territory more often now that the new Matterhorn gas pipe from the Permian to the Houston area was in service.

Waha prices first averaged below zero in 2019. It happened 17 times in 2019, six times in 2020 and once in 2023.

SUPPLY AND DEMAND

Financial group LSEG said average gas output in the Lower 48 U.S. states eased to 101.7 billion cubic feet per day (bcfd) so far in October, down from 101.8 bcfd in September. That compares with a record 105.5 bcfd in December 2023.

On a daily basis, however, output was on track to drop by 2.3 bcfd over the past three days to a preliminary two-week low of 101.0 bcfd on Thursday. Analysts noted preliminary data was often revised later in the day.

Meteorologists projected the weather in the Lower 48 states would remain warmer than normal through at least Nov. 15. But even warmer-than-normal weather in early November is cooler than warmer-than-normal weather in late October.

So with seasonally cooler weather coming, LSEG forecast average gas demand in the Lower 48, including exports, would rise from 99.5 bcfd this week to 100.9 bcfd next week. The forecast for next week was lower than LSEG's outlook on Wednesday.

The amount of gas flowing to the seven big U.S. LNG export plants rose to an average of 13.1 bcfd so far in October, up from 12.7 bcfd in September. That compares with a monthly record high of 14.7 bcfd in December 2023.

Reporting by Scott DiSavino; Editing by Kirsten Donovan

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