A quick update.  This morning’s NAM cranks out 0.46  water as the QPF  late tonight and joins the NAVGEM  with the western extent of the precipitation well west of PHL.

However, this will fall as a mix of rain changing to wet snow that may only stick to grassy surfaces in the city, maybe some accumulation north and west.  This set up will be impossible to predict snow accumulations. Too many variables and too many unknowns.

Will update tonight.

Thursday 7 PM:  This afternoon’s NAM increased the QPF to 0.60 inches water(!).  It’s a good thing it won’t all fall as snow.   The NAM also increased the cold flow, so some accumulation may occur, even in Philadelphia.   But how much falls as rain, a mix, and wet snow is still impossible to calculate.    Add to the uncertainty the ground temperature (which has warmed over the past several days) and we only know that some snow will fall, but accumulations will only be a guess.    The NAM consistently ends the snow by 7 AM.

I’ll update when the next NAM data comes available about 9:50 PM