Boundary layer clouds play an important role in the global energy budget. The radiative properties of these clouds depend upon the cloud fraction and the horizontal variability of liquid water path within patches of unbroken cloud. A simple statistical model for describing the probability distributions of liquid water path and cloud fraction in low clouds has been developed. The model is shown to reproduce realistically the diurnal cycle in the cloud fraction and horizontal inhomogeneity of marine stratocumulus. Further, the model produces realistic statistics for the horizontal variability of liquid water path within boundary layer clouds. The modeled distributions of cloud liquid water path depend upon the cloud fraction, similar to Landsat retrievals. The results are discussed in the context of improving the representation of boundary layer clouds in large-scale models.¿ 1997 American Geophysical Union