UK GAS-Within-day price firms as cold snap lifts demand

LONDON, April 25 (Reuters) - The British gas price for immediate delivery edged higher on Tuesday morning, as colder weather led to strong demand and a slightly undersupplied gas system. * British within-day contract up by 0.20 pence to 40.45 p/therm at 0822 GMT. * Traders said colder-than-usual temperatures had led to an increase in gas demand. * "It is requiring a significant amount of storage to balance the system as demand is quite high due to the unusually cold spell," a gas trader said. * Gas system slightly undersupplied, with demand forecast at 279.7 million cubic meters (mcm) and flows at 273.2 mcm/day, National Grid (LSE: NG.L - news) data showed. * Demand is almost 26 percent higher than the seasonal norm of 222 mcm, the data showed. * Britain's Met Office said in a daily webcast some parts of Scotland and northern England could see snow on Tuesday but that temperatures are likely to turn milder towards the end of the week. * The cold weather also lifted wholesale electricity prices. * British day-ahead baseload power price up by 3.35 pounds to 43.75 pounds per megawatt hour (MWh). * Four of Britain's 15 nuclear reactors, with a combined capacity of 2.3 gigawatts are offline. * Day-ahead gas price down by 0.10 pence to 40.40 p/therm. * Traders said the day-ahead price slipped as it has been higher on Monday to reflect Tuesday's tight system. * May gas contract down by 0.05 pence to 39.45 p/therm. * Day-ahead gas price at the Dutch TTF hub up by 0.08 euro to 16.35 euros/MWh. * Benchmark Dec-17 EU carbon contract down by 0.03 euro to 4.61 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)