An unusually early season, high impact winter storm is likely to affect the mid-Atlantic and northeastern states this upcoming Saturday.
The rain has come to an end across the area this evening as the cold front has shifted south. Spots in the higher elevations of northwestern NJ and the Hudson Valley saw their first snowflakes mix in before the precipitation ended. Cold air continues to pour in on north winds and everywhere is heading for a low near or below freezing tonight. This chilly airmass will set the stage for an interesting weekend.
All of the computer models today have converged on a strong nor’easter taking the textbook track up the east coast on Saturday. With a winter-like upper level weather pattern established, a strong wave will dig into the eastern U.S. and produce a rapidly strengthening area of low pressure that promises to bring its share of wind, rain and yes, heavy wet snow to many areas that should not have to think about that for a few more weeks.
Rain will initially move in from south to north on Saturday morning. As the coastal low deepens it will draw cold air southward, but more importantly produce heavy precipitation that will bring cold air down to the ground from the upper levels. This will be the mechanism to change the precipitatiomn over to heavy wet snow during the afternoon first in the Poconos/northwest NJ, and gradually sweeping eastward towards moving towards the evening. Just how much snow accumulates thereafter (and it will in many areas) is the question and a difficult forecast that will rely on a combination of factors. These include ground temperatures, elevation, proximity to the warm (60 degree) ocean and exactly where the heavy bands of precipitation set up (the exact storm track). One thing I will say is that if this was occurring in December and we didn’t need to worry so much about these above factors, then we would be looking at a region-wide 10 inch + snowstorm easily.
As it stands we have a good shot to see a historic, possibly unprecedented early season event in many areas. This includes Newark and New York City* which could see a couple of inches. Amounts will probably shade down to a coating at the beaches and increase dramatically as you head inland. The biggest concern with the event will be the heavy wet snow accumulating on trees, the majority of which still have leaves on them. There is likely going to be downed tree limbs and power outages across the region on Saturday. I will wait another day to make an accumulation forecast since this has a very high bust potential.
*A historical side note: Record October snowfall for Newark, NJ and Central Park is only 0.3” and 0.8” respectively. You have to go back to the mid-late 1800s to hear of snowfalls greater than 1 inch by these climate stations. Other immediate surrounding areas have managed 1-3 inch events with the occasional tree-snapper in the north and west suburbs.