As mentioned in last night’s post, the models have a small low pressure system developing and moving along the stalled frontal boundary that will be to our south late Sunday night into Monday.  Some snow expected in Philadelphia, although ground temperatures will be warm proceeding the storm, so not much is expected on roadways.

Both the NAM and GFS have temperatures cold enough, with dynamic cooling for rain to change to snow. QPF values have been somewhat decreasing with each model run.  NAM QPF is about 0.34 inches water, but not all of this will fall as snow.

In favor of some accumulation is the fact that much will fall before sunrise, eliminating April solar insolation effects.

A coating to 2.5 inches possible in the immediate PHL area, as measured on grassy surfaces.  Here’s the NAM and GFS snow total predictions:

 

 

As always, the NAM has higher QPF than the GFS and higher snowfall totals.   An average of the two is a best bet with a lean towards the NAM.  (With these Spring storms, the model snowfall prediction is likely better than any thing I can calculate. )

I’ll update this evening  around 10:30 PM or so.