This video demonstrates how LuckGrib makes it easy to compare two GRIB forecasts. These two forecasts were issued at around the same time, but are based on different computer models - in this case, the GFS and CMC models.
The technique of comparing two models demonstrated can also be used to easily watch to see how a forecast changes over time, by selecting a forecast time and then switching to different files from the same model. For example, if you have four days of GFS data, you can easily see how the forecast has changed for a particular forecast time using these techniques.
The Grib file librarian in LuckGrib makes this process very fast and easy.