TOW as a Variable of temperature?

[LOKE]

Running some numbers with everything unchanged except for temperatures on a 24 K 737-700.

I get - a 151 LB reduction as a Field Length Limit going from 54 Degrees F - to 55 Degrees. Climb Limit, Obstacle or any other limits are not a factor. No bleeds, flaps, brakes, RWY conditions, pressure alt - or anything elsae was changed.

These are flat rated engines and the temps are well below the temp where the engine power would vary.

So - was the 151 LB reduction due to the very small increase in TAS resulting in a bit more distance required for RWY - or is there another factor I'm missing?

Thanks for any info,

LL