UK GAS-Prompt prices flat, curve lower on strong sterling

* UK gas market broadly balanced

* Sterling up against the euro

LONDON July 15 (Reuters) - Prompt gas prices were largely flat on Friday morning as supply was expected to meet demand, leaving the market balanced, while curve prices slipped due to gains for sterling against the euro.

Gas for immediate delivery was flat at 32.90 pence per therm at 0843 GMT.

With supply flows at 188.3 million cubic metres/ day (mcm) and demand expected to be 186.9 mcm/day, Britain's gas system was almost balanced, National Grid (LSE: NG.L - news) data showed.

Total E&P's St Fergus gas terminal is experiencing an unplanned outage on Friday, with flow loss at 6 mcm/day, but normal flows are expected by Saturday.

UK-based consultancy Energy Aspects said the latest weather forecasts suggest cooler weather across Britain and northwest Europe than previously expected, with temperatures falling below the seasonal norm on several days over the next two weeks.

Further out on the curve, the August contract slipped 0.22 p/therm to 34.18 p/therm, while the Winter 16 contract fell 0.15p/therm to 43.35p/therm.

"Sterling, building on the gains seen yesterday against the Euro together with carbon markets moving lower is weighing on monthly prices," said Marcel Boonaert, head of gas trading at Wingas UK.

Sterling hit a two-week high on Thursday on expectations that the Bank of England will ease policy soon after surprising many in the markets earlier by leaving interest rates unchanged.

The British currency was up around 0.3 percent against the Euro on Friday morning.

In Europe's carbon market, the front-year EU allowance price was down 0.10 euro at 4.68 euros per tonne.

Carbon prices have fallen almost 20 percent since Britain voted to leave the European Union on June 23 on fears the country, which is a major buyer of EU carbon allowances, could also leave the bloc's Emission Trading System.

In the Netherlands, the day-ahead price at the TTF hub was down 0.15 euro at 14.10 euros per megawatt-hour. (Reporting by Susanna Twidale; editing by Nina Chestney)