The CloudSat Snow Proﬁle product (2C-SNOW-PROFILE) provides estimates of vertical proﬁles of snowfall rate along with snow size distribution parameters and snow water content for radar reﬂectivity proﬁles observed by the CloudSat Cloud Proﬁling Radar (CPR) which, based on an evaluation of the proﬁle and ancillary data, appear to coincide with snow at the surface. For these proﬁles, the product also estimates snowfall rate at the surface. Because of ground clutter, the CPR cannot reliably measure reﬂectivities near the surface. To overcome this limitation, the product algorithm estimates snow properties using a truncated reﬂectivity proﬁle, terminated somewhat above the surface, then uses the estimated snow properties in the bottom-most portion of the proﬁle to estimate the surface snowfall rate. For the truncated reﬂectivity proﬁle, proﬁles of size distribution parameters are retrieved using an optimal estimation algorithm which incorporates a priori information about snow microphysical properties, radar scattering properties, and size distribution parameters. Retrievals are performed only for proﬁles which appear likely to contain snow at the surface, either dry snow or snow with a small melted mass fraction. The retrieved size distribution parameter proﬁles and the a priori information are then used to calculate proﬁles of snowfall rates and snow water contents. The optimal estimation method produces uncertainty estimates for the retrieved size distribution parameters, and these uncertainties are then used to estimate uncertainties for the snowfall rates and snow water contents.