UK GAS-Prices rise on short system and lower temperature forecasts

May 18 (Reuters) - British wholesale gas prices rose on Thursday due to an undersupplied system and expectations of lower temperatures. * British day-ahead gas price up 0.30 pence to 41.00 pence per therm at 0848 GMT. * Within-day contract 0.40 pence higher at 41.50 pence per therm. *"The system is currently short and temperatures will be lower tomorrow," a UK gas trader said. * Average temperatures on Thursday could reach 18 degrees Celsius in southern Britain, but will fall to 13 degrees C on Friday, UK Met Office data showed. * "(There are) more buyers than sellers as players were short and the revision in the balance prompted them to cover shorts," another gas trader said. * The UK gas system was slightly undersupplied with demand forecast at 196.2 million cubic metres (mcm) and flows at 190.6 mcm, National Grid (LSE: NG.L - news) data shows. * Exports through the InterconnectorUK to continental Europe are up around 26 mcm/day. This should rise back towards 45 mcm/day next week due to lower demand, Thomson Reuters (Dusseldorf: TOC.DU - news) analysts said. * Peak wind power output is forecast at 1.2 gigawatts (GW) on Thursday, rising to 1.7 GW on Friday, National Grid data shows. * British day-ahead baseload power fell by nearly 2 percent to 43.40 pounds per megawatt hour. * Further along the curve, the June gas contract was up by 0.20 pence at 37.70 p/therm. * Day-ahead gas price at the Dutch TTF hub inched up by 0.15 euro to 15.65 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract up by 0.06 euro to 4.64 euros a tonne. * Thomson Reuters analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Lefteris Karagiannopoulos in Oslo; editing by Nina Chestney)