Hi Jason,
I know nothing about pygrib, but usually Python is case-sensitive.
Look again at the upper-case and lower-case letters in the original file:
1:0:d=2017022812:RH Relative Humidity [%]:2 m above ground:57 hour fcst:
2:227081:d=2017022812:TMAX Maximum Temperature [K]:2 m above ground:54
I have a grib2 file. You can see the components of this grib2 file below:
wgrib2 -v chart_2017022812_0057.grb2
1:0:d=2017022812:RH Relative Humidity [%]:2 m above ground:57 hour fcst:
2:227081:d=2017022812:TMAX Maximum Temperature [K]:2 m above ground:54-57
hour max fcst:
3:486870:d=2017022812:U
