Last night’s models continue to show the heaviest snow to occur from 7 AM to 1 PM today.  That said, the NAM is still showing the heaviest snow (0.40 QPF) while the GFS and the National Blend of Models (NBM) are in the 0.20 QPF range.

I’m beginning to think the NAM is the outlier for PHL and perhaps even more so north and west of PHL.  If the NAM is correct, we will get another 4-5 inches of snow on top of what we’ve gotten.

BUT, If the others are correct, we will get only 3 more inches of snow on top of what’s already fallen inthe immediate PHL area.

Areas north and west will get much less, areas south and east, much more.

With such cold/dry air poised to enter from the northwest and the edge/boundary conditions that the models are attempting to get right, the accuracy of the snow depth forecast for this storm may be lower than usual.

This is the first storm where the NBM statistics have become available outside of the NWS research groups.  The NBM is a statistical post-processing of multiple “ensemble” (statistical variations) of several models, particularly the GFS and the Canadian.  It is touted as being the forecasting approach of the future.   We’ll have to see how good it is for this storm.  So far, it’s looking good.