UK GAS-Prompt prices rise as weather cools

* System 9 mcm long -National Grid (LSE: NG.L - news)

* Met Office forecasts fall in temperatures

Nov 13 (Reuters) - British gas prices rose on Friday as cooler temperatures pushed up demand for heating.

Gas for within day delivery rose 0.25 pence per therm to 34.00 pence per therm by 1015 GMT.

Temperatures fell to their lowest level all week on Friday, causing demand to jump to around 250 million cubic metres (mcm), from Thursday's 232 mcm, National Grid data showed.

The system was 9 million cubic metres (mcm) long, however, with supply at 259 mcm, the data showed.

"Prompt contracts are building on the gains seen through yesterday's session, with a further fall in temperature forecasts driving contracts across the balance of winter higher," Marcel Boonaert, head of trading and portfolio at Wingas UK, said.

Britain's Met Office forecast temperatures dropping to between 7 to 12 degrees across the UK on Friday, in line with seasonal norms, after a very mild start to the month.

Norwegian gas flows via the Langeled pipeline, Britain's main subsea import route, were nominated at 57 mcm, an increase from Thursday.

Gas prices for December rose 0.25 pence to 37.10 pence/therm.

In the Netherlands the day-ahead gas price at the TTF hub was up 0.05 euros to 16.25 euros per megawatt hour.

In Europe's carbon market the benchmark EU Allowance (EUA) edged down 0.01 euros to 8.36 euros a tonne. (Reporting by Sarah McFarlane; Editing by William Hardy)