Simulated 21st century changes in the Great Plains low-level jet (GPLLJ) forced by greenhouse gas increases in the current generation of coupled GCMs are diagnosed, and the implications for Midwest hydrology are evaluated. Output from 18 coupled GCMs, which were run for the IPCC Fourth Assessment, are examined and 6 models with reasonably accurate simulations of the jet in 20th century simulations are selected for further analysis. All of these models project an increase in the intensity and northward extension of the GPLLJ in spring (April, May, and June) during the 21st century. The cause of the springtime intensification of the jet is consistent across the 6 models, being associated with an increase in the strength and westward repositioning of the North Atlantic subtropical high that places stronger zonal geopotential height gradients across the central U.S. Many, but not all, of the models also simulate a stronger jet in the summer and fall. Consequences of a stronger springtime GPLLJ for Midwest hydrology are implied, since a stronger jet is observed to be associated with enhanced MCSs and convective activity, and with flooding. But the coarse resolution of the GCMs impedes making connections between the dynamics, which is explicitly solved for and resolved in the model, and convective activity, which is parameterized and not resolved. As a consequence, and perhaps because of other factors operating in the models, the precipitation response is not as consistent across the models as is the dynamical response. However, an examination of the larger-scale stability characteristics in the simulations through a moist static energy analysis reveals that the intensification of the GPLLJ in the spring causes higher levels of static instability across the central U.S. in association in increased moisture advection by the jet.