Characterizing far-field high energy laser (HEL) propagation during laser weapon system (LWS) test events in an open-air environment is challenging due to many variables that affect laser transmission. These influencing variables can be divided into two different categories, the first of which is the test architecture and LWS configuration. Missions to be accomplished by the system under test (SUT) have varying degrees of difficulty, which include fast-moving dynamic targets. The SUT may also have various operating modes, wavelengths, and shifting internal optics. The second category is the underlying physics occurring from inside the laser cavity and along the optical path to the target. Phenomena including—but not limited to—cavity stability, optical physics, optical turbulence, atmospheric absorption and scattering, and thermal blooming will affect laser propagation and the characterization methodology for an LWS. It is important to consider all these factors as weapon systems are tested and scored to requirements and performance specifications for assessing lethality and effectiveness. Therefore, a year-long measurement study was conducted on the Potomac River Test Range (PRTR) to assess the optical turbulence conditions of the laser range in support of LWS test and evaluation (T&E) events. Experimental data is analyzed for averaged optical turbulence seasonal trends on a complex nonuniform range. The results are used to coordinate optimal test event timing, predict a laser’s far-field properties at the laser termination site, and generate atmospheric forecasts in conjunction with HEL and atmospheric modeling software. The results will contribute to improving future HEL testing methodology and examining accuracy of models producing optical turbulence calculations.