A microphysical model for PMC formation was run within the SHARC Atmosphere Generator (SAG), a stand-alone set of empirical models used to generate atmospheric profiles for IR radiance codes. The PMC model determines the saturation ratio of water vapor over ice for a range of altitudes and conditions of interest. Model results are compared to PMC observations in the infrared by the MSX SPIRIT III radiometer. Infrared measurements of PMC were recorded in two long wavelength infrared (LWIR) radiometer bands, 11.1 to 13.2 and 18.1 to 26.0 microns, on several occasions in the northern polar region during July 1996. Recent studies based on the refractive index of water ice have shown that PMC radiance in these LWIR bands is relatively insensitive to the solar scattering angle and only moderately dependent on temperature, which allows straightforward interpretation of the MSX observations. PMC radiance in the 11.1 to 13.2 micron band was much greater than ambient background levels, facilitating detailed comparison between model prediction and IR measurement. These and other predictive results will be presented.