Current state-of-the-art models of dust lifting in Mars climate models track finite surface-dust reservoirs but use a constant lifting coefficient at all locations until the reservoir is exhausted (e.g. Newman and Richardson, 2015). In this work, the MarsWRF General Circulation Model (GCM) is modified to adjust the dust lifting coefficient as a function of a dust availability parameter that varies with location. A “Dust Cover Index” derived from remote albedo observations is used to limit the availability of dust on the surface, without limiting the total mass of dust in the reservoir. Simulations with a two moment scheme (Lee et al., 2018) are compared with a nominal case where the unlimited dust is equally available across the planet. Idealized simulations are then used to show that the spatial location of dust availability controls the timing of large dust storms during the annual storm season, and this relationship may be inverted to provide a weak constraint on the lifting locations that lead to observed dust storms on Mars.