UK GAS-Prices mixed on weaker carbon, IUK pipe return

April 30 (Reuters) - British wholesale gas prices were mixed on Tuesday, with the day-ahead contract boosted by the planned return of the IUK pipeline between continental Europe and Britain the next day, while other contracts declined on weaker carbon emission prices.

* Day-ahead gas was 1.30 pence higher at 34.50 p/therm.

* Within-day gas fell by 0.25 pence to 34.25 pence per therm by 0819 GMT.

* The planned return of the IUK pipeline on Wednesday will open the way for gas exports, moving the day-ahead price upwards, a British gas trader said.

* The IUK pipeline, which can export and import gas, started its annual shutdown for maintenance on April 21.

* During the pipeline's shutdown, excess gas was being injected into storage instead of being exported to continental Europe.

* "Day-ahead is up on IUK, but prices (are) generally weaker across the board on carbon and coal," the trader said, explaining the decline in other contracts.

* The benchmark Dec-19 EU carbon contract was down 0.36 euro at 26.02 euros per tonne.

* The May gas contract was down 0.20 pence at 33.75 p/therm.

* The system was largely balanced on Tuesday. Gas demand in Britain was forecast at 205.5 million cubic metres (mcm) and flows at 205.2 mcm/day, leaving the system only 0.3 mcm short, National Grid data showed.

* Piped gas imports to Britain remained low. The country, however, continues to receive a strong stream of vessels carrying liquefied natural gas (LNG).

* Norwegian gas flows to Britain fell slightly, to 36 mcm/day from Monday's 39 mcm/day.

* Britain received one LNG tanker on Tuesday and expects one more during the day. Five more are due by May 5.

* Average daily temperatures in Britain are forecast at 10.3 degrees Celsius on Tuesday and, despite a slight increase the next day, are seen falling to 7.8 C at the weekend. (Reporting by Lefteris Karagiannopoulos in Oslo; Editing by Dale Hudson)