A combined physical-numerical modelling approach has been used to analyze flat-fan water sprays common in water atomization of metals, where a molten metal stream is impinged by a number of high-pressure water sprays. Due to the energy transfer at the impingement zone, the molten metal stream breaks up into droplets that ultimately become powder. In this study, a lab-scale setup was built to carry out high-speed imaging of a high-pressure, low flowrate spray. Digitally-analyzed shadowgraphs were used to determine the characteristics of the flat-fan spray, acting as inputs for predictive modelling of water spray droplet formation after primary breakup, using previous models in the literature. The spray droplet diameter after primary breakup was calculated numerically and compared with experimental measurements. A good agreement exists between experimental, theoretical, and previously-published numerical results after accounting for thinning of the liquid sheet due to radial divergence of the fan. The initial development of an industrial tool for predicting water droplet size is presented, with more features to be included in the future.