A statistical model has been developed which predicts the probability of observing a clear line of sight through a cloud scene. The basic model is P(θ) = P(0) exp(1 + k2 tan2θ)½,where θ is the viewing angle measured from the vertical, P(0) the probability of observing a clear vertical line of sight through the cloud scene, and k the “buildup” parameter, roughly the ratio of the heights to the diameters of the clouds in the scene. For cumulus clouds, k may range from 0.6 to 1.5. This model is applicable to more than one type of cloud cover and has a minimum of parameters. However, it has not yet been adequately tested. Abstract A statistical model has been developed which predicts the probability of observing a clear line of sight through a cloud scene. The basic model is P(θ) = P(0) exp(1 + k2 tan2θ)½,where θ is the viewing angle measured from the vertical, P(0) the probability of observing a clear vertical line of sight through the cloud scene, and k the “buildup” parameter, roughly the ratio of the heights to the diameters of the clouds in the scene. For cumulus clouds, k may range from 0.6 to 1.5. This model is applicable to more than one type of cloud cover and has a minimum of parameters. However, it has not yet been adequately tested.