This poster will describe the current effort at the CIMSS/SSEC/UW-Madison to develop an accurate and efficient clear sky forward model for GIFTS (and other high spectral resolution sensors) with the various features required for atmospheric profile and surface property retrieval and radiance data assimilation in a NWP context. This includes development and validation of the underlying line-by-line absorption and radiative transfer models, efficient and representative parameterization of the line-by-line results, and development of analytical jacobians and adjoints of the parameterized model.