UK GAS-Prompt prices rise on lower Norwegian supply

* Dau-ahead gas up 0.40 p at 34.30 pence/therm

* Gas system 19.4 mcm undersupplied

June 10 (Reuters) - British prompt gas prices rose slightly on Friday morning due to lower supplies from Norway.

Gas for day-ahead delivery was 0.40 pence higher at 34.30 p/therm at 0803 GMT compared to the previous settlement. Gas for weekend delivery was up 0.60 pence at 33.95 p/therm.

National Grid (LSE: NG.L - news) data showed demand was forecast at 167.4 million cubic metres (mcm) and flows a 148.0 mcm, meaning the system was 19.4 mcm undersupplied.

Physical flows of gas from Norway through the Langeled pipeline are at 19 mcm/day, slightly lower than 24 mcm/d on Thursday, due to outages at the Troll and Kvitebjørn fields.

There is also an unplanned outage at Norway's Valemon field, which is likely why flows through the Vesterled pipeline from Norway were also low.

Further along the curve, gas for winter delivery was 1.40 pence lower at 39.00 p/therm.

UK-based consultancy Energy Aspects said it has raised its average Q3 price forecast to 32 p/therm from 27 p/therm to reflect higher fuel switching price levels over that period.

It (Other OTC: ITGL - news) also revised its Q4 average price to 33 p/therm from 28 p/therm on expectations that Q4 prices could trade higher than Q1 2017 prices if there is normal winter weather but LNG supply continues to rise.

In the Netherlands, the day-ahead gas price at the TTF hub was down 0.37 euro at 13.95 euros per megawatt hour.

European front-year carbon allowances were down 0.15 euro at 5.97 euros a tonne.

(Reporting by Nina Chestney)