On May 21, 2015 at 1500 UTC, the Gridded Lightning Strike Density Product 
became operational. The grib2 data can now be found in the following
location (both links go to the same place): 

http://ftp.opc.ncep.noaa.gov/grids/operational/lightning_density

or

ftp://ftp.opc.ncep.noaa.gov/grids/operational/lightning_density