The GPM Ground Validation Doppler on Wheels (DOW) OLYMPEX dataset was obtained by a dual-polarization and dual-frequency X-band mobile radar operated by the Center for Severe Weather Research (CSWR) during the Olympic Mountain Experiment (OLYMPEX) campaign. The DOW was deployed in the Chehalis Valley for the OLYMPEX field campaign with the goal of obtaining radar reflectivity observations of precipitation in order to better understand the orographic enhancement of precipitation during frontal passages over mountain ranges. The DOW radar uses two 250 kW transmitters with a measurement range of roughly 60 km. CF-Radial data files are available from 06 November 2015 to 15 January 2016 in the netCDF-4 file format. There is 1 radar volume per file representing 10 minutes of data.