I’ve had a chance to review the 2 PM run of the NAM model as well as the latest HRRR (High Resolution Rapid Refresh) which is derived from the NAM.  Here’s what I’m seeing:

The QPF values continue to increase, now almost 1.80 inches water.  However, the upper atmosphere is expected to warm up to levels that typically don’t support snow, not only in Philadelphia, but also in the immediate suburbs to the north and west of the city.

(Areas near Reading, Allentown, and  Lancaster will have all snow.)

For a large period of time with the heaviest precipitation, from 5 AM to 9AM, I think the precipitation may fall as a mix of sleet and freezing rain instead of snow.   I believe that this will significantly reduce the snow totals in Philadelphia and the immediate suburbs to the north and west.  Even areas as far north as Trenton, NJ and Doylestown will have the same issue with freezing rain/sleet instead of snow.

It will turn back to snow before ending around 1 PM, but the heaviest precipitation will have passed by.

With snow going to sleet and freezing rain, and with high winds,  it won’t any less of a serious storm, but I’m beginning to think that snowfall totals in Philadelphia and the immediate surrounding suburbs to the north and west may only be 7-10 inches by the time the precipitation tapers down in the early afternoon. 

Areas south and east of the city will get significantly less.

The afternoon runs of the NAM can be fickle, so we really have to wait for the next model run. The next NAM model data becomes available after 10PM and I’ll update this site by 10:30 PM.