UK GAS-Prompt rises as storage withdrawals drop, demand seen higher

* System roughly balanced, UKCS output at multi-week high

* Imports from Norway rise to compensate for storage cut

March 23 (Reuters) - British gas prices for prompt delivery rose on Wednesday as storage site withdrawals fell sharply and higher next-day demand outlooks helped support sentiment.

Gas for immediate delivery rose 0.30 pence, or 1.05 percent, to 28.75 pence per therm by 0949 GMT, while the day-ahead contract gained 0.05 pence, or 0.17 percent, to 28.65 pence/therm.

Britain's gas system was oversupplied by 1.9 million cubic metres per day (mcm) with demand forecast at 276.8 mcm/day, National Grid (LSE: NG.L - news) data showed.

Withdrawals from Britain's largest gas storage site Rough dropped to zero from around 23 mcm/day overnight, with flow reductions via St Fergus Shell and the St Fergus Mobil terminal further tightening supply, real-time flow data showed.

But Norwegian imports through the Langeled pipeline, Britain's main gas import artery, rose to compensate for disruptions, to just over 70 mcm/day from slightly below 60 mcm on Tuesday.

Domestic gas output from the UK Continental Shelf rose to multi-week highs of 148 mcm/day, according to Thomson Reuters (Dusseldorf: TOC.DU - news) analysts.

Heating demand rose by 6 mcm/day to 176 mcm and was expected to climb by an additional 13 mcm on Thursday, analysts said.

Gas prices elsewhere on the curve were little changed.

The month-ahead April gas contract traded 0.02 pence higher at 28.57 p/therm, while the winter 2016-17 contract was 0.10 p/therm lower at 33.30 p/therm.

"Prices across the NBP (Shanghai: 601018.SS - news) are offered largely level with yesterday's close," said Marcel Boonaert, head of trading and portfolio at Wingas UK.

"Confirmation of an additional LNG shipment due into South Hook on the first of April improves supply outlooks for the front-month contract," he said.

Britain is set to receive the Al Kharaitiyat LNG tanker from Qatar on around April 1.

The Dutch day-ahead gas price fell 0.15 euro/MWh, or 1.23 percent, to 12 euro/MWh.

In the European carbon market, front-year allowances eased 0.04 euro, or 0.83 percent, to 4.79 euros per tonne. (Reporting by Oleg Vukmanovic in Milan; editing by Jason Neely)