UK GAS-Prices slide on supply glut, oil rout

* System long 40 mcm - National Grid (LSE: NG.L - news)

* Oil falls 3 pct, nears $30 a barrel

* Langeled pipeline flows at maximum capacity

LONDON, Jan 12 (Reuters) - British gas prices fell on Tuesday under the weight of ample supply, including strong Norwegian flows, and falling oil prices.

Gas for immediate delivery traded down 1.65 pence or 4.9 percent at 32.40 pence per therm as at 0913 GMT, while the day-ahead contract was down 0.55 pence at 33.10 pence per therm.

Britain's gas system was oversupplied by 40 million cubic metres (mcm), with demand forecast at 307 mcm and supply at 347 mcm, according to National Grid data.

"Overall the market dynamics continue to look weak," Alfa Energy said in a report published on Tuesday.

Temperatures in Britain are forecast to remain below seasonal norms for the coming week, increasing demand for gas for heating.

The Met Office forecasts highs of 7 or 8 degrees Celsius on Tuesday, with strong winds.

Wind power output was expected to peak at 5,327 megawatts on Tuesday.

Strong imports from Norway's Langeled pipeline helped buoy supply, with flows around its maximum capacity of 72 mcm.

Further along the curve, gas for February was trading down 1.05 pence or 3.1 percent at 32.75 pence per therm, as falling oil prices put pressure on gas.

Crude oil fell 3 percent on Tuesday, heading towards $30 per barrel and levels not seen in over a decade, with prices down around 20 percent since the start of the year.

In the Netherlands, the day-ahead gas price at the TTF hub fell 0.38 euro to 14.10 euros per megawatt-hour, while in the European carbon market, front-year allowances eased by 0.09 euro to 7.08 euros a tonne. (Reporting by Sarah McFarlane; Editing by Dale Hudson)