By Meteorologist John Cifelli
Good morning, and welcome to the last nice day for quite some time! I’m writing this update before retiring for the evening with the expectation that you are finding it upon waking Tuesday morning, so let me quickly discuss a couple points of information and update my thinking. First off, we are running warm tonight, about five or six degrees above forecasted at this point. Dewpoints are higher than forecasted as well. I mentioned yesterday that storms form along and tend to follow areas of higher temperature gradient, and I will be interested to see if lingering warmth along the coastal plain will encourage a more westerly track for our storm on Wednesday.
Timing looks about the same with precipitation beginning before or around dawn on Wednesday, south and east first, as rain. Temperatures quickly cool below freezing almost aloft statewide, except for at the surface as precipitation begins. This means that snow will fall through most of the column above us, but melt in warmer air just above the surface at first. There are a few ways that low level warmth can be overcome so that snow reaches the ground, including intensity of snowfall (too many snowflakes for the atmosphere to melt) and dynamic cooling (vertical motion or “lift” associated with low pressure centers lowers temperature of rising air).
I finished yesterday’s note with a comment about track and intensity, and how the type of precipitation depends on them. To complicate this forecast, I would not be surprised to see a westerly, warmer track than currently projected for the reason mentioned above, and also because of some developments in how the models are handling the upper level features behind our Wednesday storm, which will be in the Great Plains on Wednesday. At the same time, our system has trended stronger, which lends to the idea that low level warmth can be overcome by system intensity.
So the picture remains not yet perfectly clear, as developments in thinking conflict with one another, clouding the correct outcome. Tomorrow will be a fun day. I’ll be on air at the 6 p.m. news with the final call. In the meantime, my best ideas for snowfall are as follows:
Parkway and east — rain, ending as wet snow, a slushy inch at best on unpaved surfaces.
Turnpike corridor — rain to snow by noon; 1-3 inches, with the 3 inches focused north and west of the highway, northern parts of Philly and Manhattan.
North and west of 202 — rain to snow by about 10 a.m.; 3-6 inches.
Sussex, Morris, Warren and Passaic counties — Perhaps a brief period of rain, changing to snow in the early morning; 5-8 inches.
Accumulating snow ends shortly after dark, but snow flurries will linger for a while.
What I am trying to depict is a mostly rain event for the coastal plain, graduating into a tight gradient of heavier snowfall totals the further north, west and higher up into the elevated parts of the state one goes. Travel is not suggested Wednesday. Even where snowfall totals are not expected to be significant, it will snow for times and not accumulate. This still affects visibility, and of course the way people act and react on the roads. Add in the anticipated volume for the holiday, and it will be difficult and possibly dangerous to be out and about Wednesday.