Tools to handle the data
The data is stored in GRIB2-files. Below is listed few possible tools to handle the data.
PanoPly
PanoPly provides an easy UI to view GRIB, NetCDF and HDF files.
Integrated Data Viewer (IDV)
Compared to PanoPly Integrated Data Viewer (IDV) provides a slightly more complicated but more versatile user interface for browsing and analysing geographical data.
GRIB-tools
Bunch of tools exist for batch processing the data:
ECMWF GRIB tools provides number of convenient command line tools to process the data. For more information, please consult their wiki:
NOAA's WGRIB2 (and WGRIB for GRIB1 files) can for example: inventory and read grib2 files, create subsets and export data to ieee, text, binary, CSV, netcdf and mysql.
http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/
Geospatial Data Abstraction Library GDAL supports GRIB as well
http://www.gdal.org/frmt_grib.html
SmartMet Server
If you are using the data in an operational manner and live in web environment, SmartMet Server is a great resource to extract the data as JSON or GML and visualize it via WMS.
For more information, please consult: https://github.com/fmidev/smartmet-server
Additional Resources
http://en.ilmatieteenlaitos.fi/numerical-weather-prediction http://en.ilmatieteenlaitos.fi/open-data-manual-forecast-models https://aws.amazon.com/public-datasets/fmi-hirlam/