The existing AHPS netCDF files available here: https://water.weather.gov/precip/p_download_new/
do not include a projection...instead they're described as being in an HRAP coordinate system. Further the data is offseted via hrap_xor/hrap_yor. If you open the file in QGIS you need to provide a projection.
What is the proj4 for AHPS netCDF files to be able to display properly in QGIS?