UK GAS-Prices firm on Norwegian supply risk after run of losses

March 10 (Reuters) - * British day-ahead gas price rise 0.33 pence to 42.38 pence per therm at 1039 GMT. * Within-day contract up 0.10 pence to 42 p/therm. * System oversupplied by 11.7 million cubic metres (mcm/day) with demand forecast at 258 mcm, and flows at 269.7 mcm, National Grid (LSE: NG.L - news) data shows. * Overnight 25 mcm fall in Norwegian imports -- now back to normal levels -- and ongoing zero flows coming from the Netherlands lent support, Thomson Reuters (Dusseldorf: TOC.DU - news) analysts said. * Relatively minor gains may also be reaction to a streak of losses across prompt UK gas contracts this week. * April gas contract up 0.33 pence to 42.45 p/therm. * Summer 2017 contract up 0.29 pence to 41.20 p/therm. * Day-ahead gas price at the Dutch TTF hub up 0.08 euros to 16.13 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract unchanged at 5.13 euros per tonne. * Thomson Reuters analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Oleg Vukmanovic in Milan; Editing by Alexander Smith)