The Mars Regional Atmospheric Modeling System is used to predict meteorological conditions that are likely to be encountered by the Mars Exploration Rovers at several proposed landing sites during entry, descent, and landing. Seven areas, five of which contain specific high-priority landing ellipses, are investigated: Hematite (two sites), Isidis Planitia, Elysium Planitia (two sites), Valles Marineris, and Gusev Crater. The last two locations are in regions of extreme topography, and the local and regional thermal circulations that result are equally extreme. Horizontal wind speeds near the floor of Valles Marineris exceed 50 ms-1. Vertical velocities near the walls exceed 40 ms-1 and penetrate 10 km in altitude above the rim of the canyon. Thermal convection is suppressed within Valles Marineris by subsidence that forms in response to the upslope flows along the canyon walls. Wind magnitudes at Gusev crater are approximately one third of those at the canyon, but horizontal wind shear is greater. Deep convective thermals are noted at the relatively flat Hematite site, where 10 ms-1 updrafts rising to heights of 5 km are not uncommon during the midafternoon. Linearly organized convective updrafts superimposed on upslope circulations dominate over most of Isidis Planitia. Hexagonal and linearly organized convection predominates at Elysium Planitia. Afternoon circulations at all sites pose some risk (significant risk in some cases) to entry, descent, and landing. Most of the atmospheric hazards are not evident in current observational data and general circulation model simulations and can only be ascertained through mesoscale modeling of the region.