Maybe the best GRIB file viewer yet.

I like Pocket Grib as it displays all the information, especially winds & waves at the same time. It can be as detailed as you wish and you can scroll through the 5 (or 8) days with the same interval. It is simple to use and well worth the $8, which covers both your iPhone and iPad.

Chantey V about PocketGrib, v1.2.9