We examine the impact of gas pressure on the transverse coherence of high-redshift (2>=z>=4) Lyman{alpha} (Lyalpha) forest absorption along neighbouring lines of sight that probe the gas Jeans scale (projected separation {Delta}rp<=500h^-1^kpc comoving, angular separation {Delta}{theta}<=30arcsec). We compare predictions from two smoothed particle hydrodynamics simulations that have different photoionization heating rates and thus different temperature-density relations in the intergalactic medium (IGM). We also compare spectra computed from the gas distributions to those computed from the pressureless dark matter.