In order to facilitate the routine NWP assimilation of operational advanced infrared sounder data (IASI on MetOp and CrIS on NPOESS) over high latitude land regions of the globe, we demonstrate a method for preparing the input to 1-D var data assimilation. The method involves the identification of clear sounder fields of view over snow/ice in winter conditions and the determination of the skin temperature and infrared emissivity appropriate for each sounder field of view. The method is demonstrated using NASA AIRS and MODIS data over snow covered land and sea ice. MODIS data collocated within AIRS fields of view are used to estimate the uniformity of the scene. Also the derived surface emissivity derived from AIRS is compared to theoretical and measured expectations of snow/ice emissivity. A clear filter is applied to the AIRS data which uses both the MODIS sub-pixel uniformity and consistency with the expected snow emissivity within certain limits. A surface temperature and infrared emissivity is derived from the clear AIRS fields of view using one or more estimation methods. Examples will be provided for selected time periods to illustrate the density of observations available for assimilation by this method.