I’ve had a chance to look at the morning’s model data. As expected, the mid levels of the atmosphere were too warm to support snow in and around PHL today.  We did have some sleet as the rain fell through colder lower levels and that could continue into the evening.

According to this morning’s profiles, the thermal profiles chill down to support snow about 6-9 am Wednesday morning, earlier north and west. Current NAM QPF is about 1.05 inches water, which in winter,  would be over a foot of snow!   In March, with all sorts of magical guessing, I can see as much as 9 inches of snow on grassy surfaces, with less accumulating on roadways by Wednesday evening.  So snow starts In the morning and continues through the day into evening on Wednesday, 

That’s my current call.  The deciding model run data becomes available between 10pm and 10:40 tonight. I’ll update then.

5 pm update- this afternoon’s NAM (“off-hour” model runs not always reliable) has increased QPF to 1.65 inches water falling as snow.  The trend is increased snow totals, possibly over 12 inches.  Have to wait for tonight’s NAM run.

A quick update-  last night’s NAM ran a bit colder in the mid levels of the atmosphere for today, Tuesday .  Expect a little more snow mixed in with rain today in PHL,  and far northern areas may get some wet snow.  Still expect little or no  accumulation today in immediate PHL area.

For Wednesday, temperature profiles support snow even in PHL. QPF still running around 0.70 water. Daytime accumulation could be  4-7 inches on grassy surfaces, less on roadways.  I’ll update this evening.