UK GAS-Prompt prices rise on milder temperatures, lower imports

LONDON, March 21 (Reuters) - Prompt British wholesale gas prices rose on Tuesday morning, as milder temperatures led to stronger demand and an unplanned outage cut imports from Norway. * British day-ahead gas up by 0.42 pence to 41.10 pence per therm at 0917 GMT. * Within-day gas up by 0.60 pence to 41.30 p/therm. * System undersupplied by 14.6 million cubic metres (mcm), with demand forecast at 273.9 mcm/day and flows at 259.3 mcm/day, National Grid (LSE: NG.L - news) data shows. * Imports from Norway through the Langeled pipeline are at around 45 mcm/day, down from over 60 mcm on Monday. * Norway's gas capacity cut by 18.4 mcm due to an unplanned outage at the Kollsnes processing plant, gas system operator Gassco said. * British weather is expected to be below the seasonal average for the next few days, Giacomo Masato, research analyst at energy and commodities brokerage Marex Spectron said. * Gas demand for heating is likely to rise. "Likewise, power demand is predicted to temporarily increase," Masato added. * Britain's Met Office forecast temperatures would struggle to get above single figures in degrees Celsius across the country on Tuesday. * Gas demand is around 4 percent above the seasonal norm of 262.3 mcm, National Grid data showed. * April gas contract up by 0.17 pence to 41.15 p/therm. * Day-ahead gas price at the Dutch TTF hub up by 0.23 euro to 15.63 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract down by 0.01 euro to 4.98 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 Susanna Twidale; editing by Nina Chestney)