Numerical model simulations of a surface cold front are used to examine the role of differential cloud cover on frontal propagation. We have explored the role of clouds by comparing simulations of an observed case using MM5 with and without cloud effects on the surface radiation budget. An interesting finding is that differential cloud cover behind the cold front produces a secondary potential temperature gradient due to differential long wave cooling. In general frontal propagation depends on model physics but is reproduced realistically in the model. Alteration of soil moisture by frontal precipitation did not have a substantial effect on frontal intensity or propagation, as demonstrated by comparing simulations with and without interactive soil moisture. We illustrate the mechanisms producing these effects through the use of detailed diagnostics of the surface energy budget.