generate_prsn not producing correct fill values

[nikola-rados]

The files output by the snowfall generation script (generate_prsn) have a strange issue with their fill values. The values themselves are the same as they in the parent pr netCDF, -32767. However, they do not mask appropriately displaying the number rather than an _. Furthermore, the metadata states that the fill values should be 32768.

I assume the issue is occurring somewhere in create_prsn_netcdf_from_source(...) but cannot say for sure. This needs to be explored further.