The RPM is not in the range of nailing down this system, and usually has a southern bias in this range so take this map with a grain of salt.  But usually it follows the other mesoscale models so I am scratching my head on this one.  The RPM shows what is going to occur with a phase though.  It shows very impressive banding and a rain to snow situation in Philly.  Similar to one in late January in 2011.  

TRENDS

A very difficult forecast is ahead for this event since we are seeing the European stop the trend and the GFS continue it.  Normally this is a no brainer and we expect the Euro to gradually lock in on a less bullish snow for areas farther south, but it is approaching a range the Euro is not the "king" in with these storms.  The GFS is taking over and continues to side towards the Euro by making some big corrections to the northern stream energy.  

EURO SNOW TOTALS BY CITY

GFS SNOW FALL TOTALS BY CITIES

GFS:

NEW

OLD

Notice how the GFS shows a much stronger northern stream s/w that digs more and leads to stronger confluent flow to the northeast.  This slows everything down and allows for a more favorable phase with the dynamic back edge extending back into Philly with heavy snow! This trend is a great one!

EURO

New Euro backs off the stronger more amped solution.  Both models got a better look at this energy today so it is weird to see the two go opposite ways on trends, but in reality they are not that far apart right now.  Just the trend stopped on the euro and the trend continues on GFS.  

Summary

Tonights runs will be big!  If the GFS holds its ground or continues the deeper northern stream idea we will see a very interesting situation from Philly on north.  If the Euro holds ground we will still see a significant snow but if it corrects more for a weaker northern stream those significant snows move northeast.