There are many past winter storms where there have been large differences between the GFS and NAM models regarding QPF (amount of precip).

By definition ( if not by other measures) tomorrow’s rain is not a winter storm, but the models differ significantly with the amount of precipitation forecast.  The NAM has been advertising 2 inches of rain for PHL, while the GFS has a light rain, less than 0.50 inches total.  That’s a giant difference.

When dealing with snowfall, the differences are obvious when a heavy precip forecast goes bust.   It will be interesting to see if the NAM or the GFS model verifies tomorrow.   Something to consider for later in the season when we likely see divergence in forecasts.