This paper shows that the variance of load bus voltage magnitude in a small power system test case increases monotonically as the system approaches a Hopf bifurcation. This property can potentially be used as a method for monitoring oscillatory stability in power grid using high-resolution phasor measurements. Increasing variance in data from a dynamical system is a common sign of a phenomenon known as critical slowing down (CSD). CSD is slower recovery of dynamical systems from perturbations as they approach critical transitions. Earlier work has focused on studying CSD in systems approaching voltage collapse; In this paper, we investigate its occurrence as a power system approaches a Hopf bifurcation.