* Gas system expected to be 10.7 mcm/d short * But LNG imports remain high * Warm weather expected for end of the week LONDON, Aug 7 (Reuters) - British prompt gas prices rose on Tuesday morning as low North Sea supplies left the system undersupplied despite healthy import levels of liquefied natural gas (LNG), analysts said. Gas prices for next day delivery rose 0.4 pence per therm between Monday and Tuesday morning to 52.40 pence per therm, while within-day prices rose 0.85 pence to 53.05 pence a therm. "Continued low UKCS production and lower Norwegian imports have led to a short system this morning giving a bullish signal for today," analysts at Point Carbon said, but added that some of these bullish factors could be offset by healthy LNG supplies and the end of some maintenance in the North Sea. Point Carbon said that it expected day-ahead prices to range between 52.40 and 52.60 pence per therm. Gas demand in Britain was expected to be 178.3 million cubic metres (mcm) on Tuesday, almost 30 percent below seasonal demand, according to data from NAtional Grid. Despite the low demand, the system was expected to be some 10.7 mcm short, with expected flows of only 167.6 mcm. Some relief will be incoming LNG volumes of around 422,000 cubic metres between August 9 and 13 and another 240,000 cubic metres already having been delivered into Britain earlier this week. In the power market, prices for baseload (24 hours) delivery on Thursday dropped 60 pence to 40.30 pound per megawatt-hour between Monday and Tuesday morning. The UK's MetOffice said that it expected slightly warmer weather on Wednesday, with maximum temperatures rising by two to three degrees Celsius from Tuesday to 23 degrees. The outlook for Thursday to Saturday was "mainly dry with sunny spells, becoming warm or very warm inland," with temperatures around 25 degrees.

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