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.

A front boundary that will move through tomorrow (Sunday) morning will stall to our south.   A wave of low pressure riding along the front will move through to our south late Sunday night into Monday morning causing snow to fall in April!

Like similar storms over recent weeks, dynamic cooling will result in enough cold air in the lower levels of the atmosphere for precipitation to turn to snow between 3 AM and daybreak.  Current QPF values are in the 0.40 inch range which translates into anywhere from 1 to 3 inches possible on grassy surfaces with some accumulation on roadways in the immediate PHL area and close to 5 inches  north  in areas around Allentown and Reading!

Temperatures warm during the day on Monday, and whatever falls will quickly melt.

Exact predicted QPF amounts have changed over the day today, so a final handle on this won’t be available until Sunday evening.

A front moved through on Friday and skies will clear for Saturday.

Saturday will be mostly sunny and almost seasonable, with high temperatures near 57.

Another cold front moves through early Sunday with some cloudiness early morning, followed by more sunshine in the afternoon.  High 57.

Overall, a nice beginning for April.

Looking at the long range model forecasts, the first two weeks of April promise to be a dynamic period with a few outbreaks of cooler weather and several periods of rain.