Clouds can have a major impact on performance and mission opportunity of ground and airborne laser weapons. Database summaries and modeling techniques are presented for the physical and optical characteristics, frequency of occurrence, and probability of cloud-free line-of-sight (PCFLOS) of mid-level and high-altitude clouds. Emphasis is on subvisual and thin cirrus due to its predominance at mid- latitude. The statistical models presented are for top-level system engagement analyses, and to generate cloud realizations for more accurate simulation. The first portion of the presentation describes the requirements and limitations of current approaches and databases used for modeling. Criteria such as period-of-record, meteorological anomalies, spatial and temporal resolution, and measurement and data collection techniques, are discussed. The next part describes the effects of variations in cloud thickness, altitude, extinction, and scatter ratio on laser weapon operations and availability. This is followed by a practical, validated method for estimating PCFLOS as a function of elevation angle based on commonly-recorded, site-specific meteorological parameters.