The within-day contract rose 0.75 pence to 43.00 pence per therm at 0845 GMT.
The day-ahead contract was yet to trade.
Britain's gas system was undersupplied by 37.8 million cubic metres (mcm), with demand forecast at 293.8 mcm and flows at 256.0 mcm/day, National Grid data showed.
Flows into the system from storage tanks fell by 32 mcm.
Flows from LNG terminals fell by a further 10 mcm, after a 24 mcm fall on Thursday, although five LNG tankers are due to arrive by the end of the month.
Two tankers have already docked at the Isle of Grain and South Hook terminals, indicating higher LNG send-out rates soon.
Total LNG send-out was 61 mcm, 30 mcm lower than at the start of the week, Eikon Refinitiv data showed.
Flows from Norway and the Netherlands are also expected to fall, by 7 mcm in total.
Gas for power demand is seen falling by 10 mcm to 50 mcm even though wind power generation is also expected to fall to 7.9 gigawatts (GW) from 10 GW the previous day.
Residential consumption, mainly used for heating, is also seen falling, by 17 mcm to 211 mcm, as temperature forecasts were increased by 1.7 degrees Celsius to 6.9 degrees.
Further out on the curve, most contracts also edged higher.
The weekend contract rose 0.60 pence to 41.00 p/therm.
The December contract rose 0.65 pence to 41.75 /therm.
The day-ahead gas price at the Dutch TTF hub slipped 0.05 euros to 15.65 euros per megawatt hour.
The benchmark Dec-19 EU carbon contract was up 0.29 euros at 24.23 euros per tonne.