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developed under phase 2 in an experiment for augmenting beneficial precipitation over an an~a of several thousand square kilometers. Developed technologies will be transferred (phase 4) to users in all applicable areas within the High Plains as they become available. Figure 1 shows these phases for both the atmospheric and the socio- economic/environmental components. The ISWS design plan is only generally formulated because, at the time of writing, there was inadequate information on the character- istics of the clouds in the High Plains, which prevented definitive specifications of many of the design features. Design concepts and definitions were tentative, based on data and findings from the relatively few experiments in the High Plains and from programs in other areas. The first 3 years' efforts in the field were directed toward developing a more thorough climatology of cloud and precipita- tion characteristics of the High Plains, toward improving our under- standing of the physics of natural clouds, and toward developing and testing the instrumentation and equipment systems and the operational procedures. Seeding calibration studies were carried out to develop and test multiple aircraft research procedures and to document ice- crystal development (and our ability to observe it) associated with seeding. By the end of 1977, a comprehensive, high-quality data base had been acquired. . In December 1977, the HIPLEX Design Workshop assessed the basis for undertaking a randomized exploratory experiment. Deliberations concerned conceptual models of cloud seeding applicable in the High Plains, our ability to identify seedable clouds, measuring crucial variables, and our abil'ity to evaluate the effects of seeding. The consensus of the workshop participants was that our understanding of cloud and precipitation processes in small cumulus congest us clouds in the Miles City area and our ability to measure the pertinent variables were sufficient to permit the start of a randomized experiment on these clouds, using the so-called static seeding procedure. The participants also suggested several analyses that should be completed before that experiment was launched. These included descriptions of the characteristics of, and measurement procedures for, principal response variables, identification of mesoscale influences on convective clouds and their response to seeding, specification of dispersion rates of ice crystals produced by seeding, determination of seeding rates needed to attain appro- priate concentrations of ice crystals and graupel, and development of multivariate and other evaluation techniques. Efforts in 1978 concentrated on obtaining information to resolve these issues. The necessary measurements were made and analyses performed, and this work provided the basis for the following detailed plan for HIPLEX-l. 3