LONDON, Dec 7 (Reuters) - British prompt gas prices gained

slightly on Friday but the system was slightly long as milder

temperatures reduced demand, offseting the impact of lower

supply from some key pipelines.

British day-ahead gas prices gained by 0.33 pence per therm

between Thursday and Friday morning, trading around 69.53 pence

at 0900 GMT, while prices for within-day delivery were unchanged

at 69.50 pence per therm.

Earlier this week prompt gas price hit a 10-month high of

71.25 pence/therm as Britain experienced colder weather,

including sub-zero temperatures in many areas and snowfall.

Gas demand on Thursday was expected to be 339.4 million

cubic metres (mcm), 24 percent higher than the seasonal norm,

according to data from National Grid, while flows seen at 342

mcm as supplies, down from Thursday.

Analysts said the outlook for prompt gas contracts was

'sideways to bearish,' although increased supply from storage

and some pipelines was offset by disruptions to others.

'The impact that the scheduled maintenance at (parts of) the

Norwegian Continental Shelf could have on flows to the UK

remains a risk factor limiting the downside of the contract,'

Reuters Point Carbon said in a daily report.

It added: 'But higher storage withdrawals and supply (of

liquefied natural gas) from Grain (LNG Terminal) could provide

flexibility if needed.'

Daytime temperatures are expected to become slightly milder

on Friday, Britain's Met Office said, adding that temperatures

would reach a maximum of 7 degrees Celsius in southern Britain

over the next few days while night time temperatures would most

likely remain above freezing.

Further long the price curve, the summer 2013 gas contract

was valued at 62.60 pence/therm, unchanged from Thursday's close

as crude oil prices were broadly steady compared with last

night's settlement, trading at around $107/barrel.

In the power markets the contract for baseload (24 hours)

delivery gained 20 cents, trading at 52.35 euros/MWh, relatively

unmoved despite an unplanned outage on Friday at EDF Energy's

660-MW Heysham 2 unit 7 reactor.

The reactor came offline at 0930 GMT on Friday, EDF Energy

said in a statement, and had only returned to the grid earlier

in December following turbine repair works.

(Reporting by John McGarrity, editing by William Hardy)

((john.mcgarrity@thomsonreuters.com))

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