UK GAS-Prompt prices mixed, cooler temperatures underpin prices

* System oversupplied by 10 mcm/day

* LNG tanker Umm Slal docks at South Hook

April 24 (Reuters) - British prompt gas prices were mixed on Friday as the system was oversupplied but forecasts for cooler weather next week offered some support.

Gas for within-day delivery was down 1.2 percent at 44.75 pence per therm, while gas for day-ahead delivery was up 0.6 percent at 45.25 pence per therm by 0931 GMT.

National Grid (LSE: NG.L - news) data showed supply was forecast at 201 million cubic metres (mcm) on Friday, while demand was seen at 191 mcm, showing the system was oversupplied by 10 mcm.

Meteorologists at Thomson Reuters Point Carbon forecast temperatures falling below normal levels next week which could drive up demand for gas for heating.

Gas flows from Norway to Britain were slightly lower after an outage at France's Dunkerque ended, increasing Norwegian flows to the continent.

"Norwegian flows into Dunkerque, which were zero most of the day yesterday due to the maintenance, are flowing at 32 mcm/day this morning," said Thomson Reuters Point Carbon analyst Marina Tsygankova.

LNG tanker Umm Slal arrived at South Hook on Friday and a steady flow of shipments was expected to continue with Al Shamal, Al Gharrafa and Al Rekayyat due next week, boosting supplies.

Further along the curve, gas for delivery next month was up 0.7 percent at 44.30 pence per therm.

In the Netherlands, the day-ahead gas price at the TTF hub was down 0.6 percent at 21.48 euros per megawatt-hour.

The benchmark European Union carbon price was trading 1.1 percent higher at 7.37 euros a tonne on ICE Futures Europe. (Reporting by Sarah McFarlane; Editing by Pravin Char)