UK GAS-Prices fall on long system

LONDON, April 6 (Reuters) - British wholesale gas prices declined on Thursday morning due to in a slightly long system. * Within-day contract down 0.35 pence at 40.60 pence per therm at 0930 GMT. * British day-ahead gas price inched down by 0.30 pence to 40.60 p/therm. * "The system looks comfortable, slightly long...no major changes in temperature (forecasts)," a gas trader said. * System slightly oversupplied by around 10 million cubic metres (mcm), with demand forecast at 261.1 mcm and flows at 271.3 mcm/day, National Grid (LSE: NG.L - news) data shows. * Exports to continental Europe through the InterconnectorUK (IUK) are nominated at 43 mcm. * Langeled flows are down at 45 mcm, likely due to an outage at Norway's Kvitebjorn gas field which has reduced Norwegian exports by 10.7 mcm. * Met Office forecasts show temperatures falling slightly on Friday before peaking at 20 degrees Celsius in the south of the country on Sunday. * Peak wind generation at 3.1 gigawatts (GW) on Thursday, falling to around 2.4 GW on Friday. * Dungeness B-21 nuclear reactor restarted on Thursday after an outage that started on March 9. * Winter 2017 contract down by 0.10 pence to 46.95 p/therm. * Day-ahead gas price at the Netherlands' TTF hub down 0.13 euro at 16.17 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract up 0.09 euro at 4.91 euros a tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Lefteris Karagiannopoulos; editing by Nina Chestney)