A major limitation of existing operational systems when applied to forecasting or synthesizing streamflow from snowmelt on watersheds in many pans of central and northern Canada is that they are incapable of accurately simulating the process of infiltration into frozen soils. The results and discussion in the paper provide a method of overcoming the problem in areas of climatic and physiographic conditions similar to those of the Prairies.Details outlining the development of a model describing snowmelt infiltration into frozen soils are presented. The model is based on the concept that for practical purposes the infiltration potential of frozen soils may be generally categorized as (1) restricted: impervious; (2) unlimited: capable of infiltrating the snow-cover water equivalent; and (3) limited: infiltration is governed by the snow-cover water equivalent and the ice content of the soil at the time of melt. An empirical relationship for calculating infiltration into frozen soils of "limited" potential is given. The improvement in performance of the United States National Weather Service river forecasting system—Sacramento model (NWSRFS) in synthesizing streamflow from snowmelt on a small watershed in western Saskatchewan gained through the use of the infiltration model is demonstrated. Different procedures of interfacing an infiltration model with an operational system, the NWSRFS, are presented, discussed, and evaluated.