A high of 40 at Philly International with sunshine giving way to clouds is not too bad for a January afternoon...
Oh wait, it's March 1st! The average high is closer to 50! Our average low should be around the freezing mark, but we reached 17 shortly before 6am. We also have an Arctic front coming Sunday evening and then a wave of low pressure shall ride along the stalled out front to provide us some snow. This is the Winter that shall never end....
Overnight lows will be in the lower 30s with a mostly cloudy sky, but come Sunday morning temperatures will rise with a southerly flow and we'll have rain(some snow/mix north and west) with highs around 40. The Arctic front will push through overnight into Monday so temperatures will drop by morning; we'll gradually see a changeover to sleet and then snow by midday Monday.
So....this looks to be set in stone, right?
Not by a long shot. I have a few "red flags" of mine below:
1) The Arctic front will provide wickedly cold AND dry air(temperatures will drop like a rock Monday morning into the afternoon); there will be a sharp cutoff with precipitation because of the air aloft cooling down and drying out within the snow growth region(~500 millibars or 18,000 feet). This will essentially set up a "brick wall" preventing moisture from spreading north of NYC.
2) Once temperatures drop overnight the atmosphere will cool from top to bottom; although Southern NJ, SE PA, and going into the Delmarva will essentially see the most QPF(quantitative precipitation forecast; basically the project amount of water equivalent) of ~1" the issue is how long will it take for the entire column of air to cool? 850 millibar(5000 feet) temperatures in the early morning are projected to stay above freezing which would mean prolonged sleet(and sleet holds ~3x's more water content than snow does).
With that said I feel that this is a light snow event north of I-78 with just 1-3" of potential snow; south of I-78, but north of Routes 30 &40(pretty much including NYC, Philly, Toms River, and Atlantic City) the potential of 3-6" exists(including sleet and) while south of Routes 30&40 may see 6-9" of snow(including periods of sleet and freezing rain....leading to ice).
Behind this system it will be very cold with temperatures barely getting above freezing on Tuesday so there won't be any chance of melting taking place.
With that said, stay tuned and be sure to look for updates on my weather page at www.scottderekwx.com/forecast.html.