This work is on synthesis of a gain scheduled controller - parameterized by the Reynolds number - for transition control in plane Poiseuille flow. In a real system, the Reynolds number is time-varying - it changes with the speed of flow. The problem considered here is to prevent the transition from laminar to turbulent flow at the very onset of turbulence, when the velocity of flow is changing with time. For this problem a gain scheduled controller , parameterized by the Reynolds number, is proposed. A linear parameter-varying (LPV) model of plane Poiseuille flow parameterized by the time-varying Reynolds number is first obtained, which is used to synthesize a gain scheduled control law.