UK GAS-Prompt prices mixed as weather set to turn colder next week

LONDON, April 20 (Reuters) - Prompt British wholesale gas prices were mixed on Thursday, with colder weather forecasts for next week supporting the day-ahead contract but within-day gas down on lower demand. * British day-ahead gas price rose by 0.15 pence to 39.25 pence per therm at 0949 GMT. * Traders cited expectations of colder weather for next week as providing support to the day-ahead contract, with further support from a slightly short system. * System undersupplied by 0.9 million cubic metres (mcm) with demand forecast at 254.5 mcm and flows at 255.4 mcm/day, National Grid (LSE: NG.L - news) data shows. * Within-day contract down by 0.15 pence to 39.25 p/therm. * "Supply has been comfortable so far with no disruptions and temperatures are milder which has reduced demand," a European-based gas trader active across multiple markets said. * He added that with colder weather expected next week and with little new LNG seen arriving in the near-term, prices should found renewed support across Europe. * Imports from Norway through the Langeled pipeline were around 50 mcm/day, up from around 48 mcm the previous day. * Supplies into the St Fergus NSMP terminal gathered pace as offshore fields returned from maintenance. * May gas contract up by 0.05 pence to 39.05 p/therm. * Winter 2017 contract down by 0.15 pence to 46.40 p/therm. * Day-ahead gas price at the Dutch TTF hub up by 0.02 euro to 16.27 euros per megawatt hour (MWh). * A Dutch court said on Thursday it had ordered prosecutors to open a criminal investigation into responsibility for earthquakes triggered by gas production at the country's large gas field in Groningen. * Earlier this week, the Netherlands set out plans to reduce production at its Groningen field by 10 percent from October to limit the risk of earthquakes. * Benchmark Dec-17 EU carbon contract down by 0.03 euro to 4.80 euros per tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting By Oleg Vukmanovic; Editing by Nina Chestney)