UK GAS-Prices down on supply disruption, Norwegian gas going to Europe

* Day-ahead down 0.13 pence at 41.70 p/therm

* UK gas system largely balanced

* Gas demand seen higher this winter y-o-y-Energy Aspects

LONDON, Sept 9 (Reuters) - British wholesale natural gas prices were slightly lower on Wednesday as domestic supplies continued to be disrupted and more gas was re-routed from Norway to continental Europe.

Gas for immediate delivery slipped by 0.05 pence to 41.90 pence per therm at 0758 GMT, while day-ahead prices eased by 0.13 pence to 41.70 p/therm.

Flows from the UK Continental Shelf have been disrupted due to several outages but are expected to increase from Thursday.

Norwegian supply is higher but a lot of the extra gas is going to continental Europe. However, the send-out of liquefied natural gas (LNG) supply is still above 40 mcm/day.

"Prices are slightly lower this morning on the bearish factor of lower UKCS flows but it's not a big fall because the market is quite balanced," a UK gas trader said.

Britain's gas flows were forecast at 174.1 million cubic metres (mcm) a day and demand at 175.7 mcm, National Grid (LSE: NG.L - news) data showed.

Further along the curve, prices for winter delivery were slightly up, trading 0.20 pence higher at 44 pence/therm.

This coming winter demand will be higher year-on-year on the assumption of colder weather, UK-based consultancy Energy Aspects said.

"Over the two winter quarters, we expect gas demand from power will be up by 0.5 billion cubic metres (bcm) and then 0.6 bcm, while overall demand will be up by 1.4 bcm and 1.5 bcm," analysts said in a note.

Supply from domestic production and Norway will be higher as a result, particularly in the fourth quarter. LNG supply will be at last year's levels in Q4 but higher by the first quarter next year.

"The UK market will see a fairly heavy call on storage to get through the winter. We put that at some 3.9 bcm, which will take UK gas in storage down to fairly low levels," Energy Aspects added.

In the Dutch TTF gas market, day-ahead prices were 0.10 euros higher at 19.48 euros per megawatt hour.

In Europe's carbon market, benchmark EU Allowances (EUA) edged down by 0.04 euros to 8.21 euros a tonne. (Reporting by Nina Chestney; Editing by Greg Mahlich)