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UK GAS-Prices up on lower LNG supply, higher exports and Rough outage

* Rough outage extended to March/April next year

* Lower LNG supply

* Exports to continental Europe rise

LONDON, July 18 (Reuters) - British wholesale gas prices rose on Monday morning in reaction to lower expected supply of liquefied natural gas (LNG), higher exports to continental Europe and the extension of an outage at the Rough gas storage site to next year.

Gas for day-ahead delivery was up 0.80 pence at 33.25 pence per therm at 0853 GMT from the previous settlement.

Flows were forecast to be 178.6 million cubic metres (mcm) a day and demand is seen at 185.7 mcm, leaving the system undersupplied by around 7 mcm, National Grid (LSE: NG.L - news) data showed.

On Friday, Centrica Storage Ltd announced that additional well testing at its Rough gas storage site would be carried out, possibly until March/April next year.

The news sent winter UK gas prices up on concerns Britain would go into winter with record-low storage levels.

Analysts said Rough should have 1.25-1.3 billion cubic metres (bcm) of gas in storage by the end of the summer, which is around 1.2 bcm less than last winter's withdrawal levels.

Prices were also higher because LNG sendout is nominated at 24 mcm/day, lower than flows of 35-38 mcm/day last week.

Exports to Europe through the InterconnectorUK (IUK) pipeline are nominated at 50 mcm/day compared to Friday's 55 mcm/day, which is close to capacity.

Thomson Reuters (Dusseldorf: TOC.DU - news) analysts expect IUK exports to be 50-55 mcm/day because the British system has only medium-range storage sites and the IUK to soak up any extra supply while Rough is out of action.

Further along the curve, gas for August delivery was up 0.74 pence at 33.54 pence per therm.

In Europe's carbon market, the front-year EU allowance price was up 0.04 euro at 4.97 euros per tonne.

In the Netherlands, the day-ahead price at the TTF hub was up 0.03 euro at 14.23 euros per megawatt-hour. (Reporting by Nina Chestney; Editing by Dale Hudson)