This is not the AccuWeather Forecast. This is my early call on Sunday’s potential storm threat.
If adjustments have to be made, the thinking at this time is that the rain/snow line would have to be pushed further north and west to start.
This mornings run (12z) on the GFS (Global Forecast System) shows almost exactly the track that I was expecting with this storm system. The trending positive NAO (North Atlantic Oscillation) will force this storm (which is riding the southern branch of the jetstream) to come north, up the coast to around Virginia Beach. This will end up being just far enough north to put the Delaware Valley in the middle of a little snow event Sunday afternoon.
The air in place is just barely cold enough to support snow with this event. However, as this storm continues to develop it will begin to manufacture its own cold air. That will keep the 540 thickness (thickness of the layer of cold air) deep enough to support snow. The 850s (temps at approx. 5,500ft.) are well below freezing to begin with so there’s no issue there. So assuming the storm pans out exactly how the GFS has is this morning it will be snowing here Sunday afternoon in Philadelphia with a mix south and east. Actually, it may start out as rain in southern New Jersey depending on the timing and exact track. That’s the very difficult part with this, positioning the rain/snow line. The issue that continues to have me biting my finger nails is the air closest to the ground. If you look at soundings the T1 level (level of air closest to the ground) is above freezing. This is because of the mild ocean air that will get pulled inland on an east, northeast wind. As the storm continues to slide off the coast, however, the air will get colder as our surface winds begin to shift out of the northwest. So this will eventually turn all of southern New Jersey over to snow as well. But it will wreak havoc with accumulations.
As far as accumulations are concerned this is NOT looking like a big snow storm for us. Not even close. The fact that the ocean temperature is very mild (45 degrees) and we now expect the storm to speed up and hit during the day (Sunday), it will be very difficult to get much of an accumulation out of this. In my mind the thinking at this time is this will end up being very similar to what happened last Saturday. It will snow, but accumulations will be mainly confined to grassy suurfaces. Also, the temperatures will probably end up staying above freezing so it will be a very wet snow. Making an early call here I would say most of the region picks up 1-3 inches of snow out of this with the exception being the immediate coast. The roadways stay wet, not white. Slick spots should be kept down to a minimum. There could end up being a more concentrated 2-3″ band that develops over the city depending on the track, but as of now I will go with only 1-3″.
It begins very early Sunday morning with snow in Philadelphia and our northwestern suburbs. A mix of rain and snow in western Burlington, Camden, Gloucester, Mercer and Salem counties and just plain rain in Cumberland, Cape May, Atlantic, eastern Burlington and Ocean counties. That mix line will push closer to the coast as the day wears on.
So this is the early call from Accu-Sowers. This is not etched in stone and could change,, but this is what I am thinking at this time. I like what the models are suddenly showing this morning. So it more then likely will be snowing Sunday afternoon, but accumulations will be kept down to a minimum and mainly be confined to grassy surfaces.
Sorry guys, no Nor’easter with this.