7:30 PM UPDATE
The models are still confused and fuzzy about the northern M/A. The 12z runs today backed off with any real snow threat from PHL to NYC. But both the 18z NAM and GFS are now much wetter and have a better surface low developing along the M/A coast. So once again trending better with the latest runs.
The 18z NAM was much colder and had more QPF's for the PHL to NYC areas at .50"-1.00" A mix of rain and snow changing to wet snow during Friday into the early evening hours. Some Accumulations are possible, surface temps are marginal in the mid 30's, so we have time to see more trends.
The 18z GFS also juiced it up some with QPF's of .50" across much of the area. The problem with the GFS is it's too warm at the surface and aloft while much of the precip is mixed or rain, and only changes to wet snow briefly before ending Friday evening. So little or no accumulation with this run.
I'll update more tomorrow and hope to have a better idea where were going with this system, as of now I'd say a mixed bag of snow and rain changing to some wet snow before ending on Friday and Friday evening. A period of light snow is also possible during Thursday AM, but little or no accumulation with this light precip. The second more substantial precip will move in during Thursday night and continue into Friday.
Monday: 7:00 PM
I'd like to say a couple things real quick about the New Years storm and this weekend.
The more I see what's going on, the more I see a very complex setup in which this could be a sneak up on you the last minute event.
This closed H5 low/energy and where it sets up is CRITICAL ! With a tremendous block developing to the north and this closed H5 low seems to want to park itself near the Northern M/A or SE New England coast. This could be troubled and a very complex setup for The Northern M/A and especially New England.
With a feature such as this (Closed H5 Low) near the coast and cold air drilling down and aloft, a captured and intense surface low nearly stalling out or even possible retrograding SW from the New England coast, can give a MET or Forecaster as myself, a huge headache.
So no way am I writing this storm off, and think we can see some accumulating snow for both PHL/NYC areas from New Years Day and possibly into Saturday.
The model solutions vs teleconnections makes me scratch my head a bit here, in saying POSSIBLY A SNEAK UP ON YOU QUICKLY, CAUTION IN FORECASTING/WORDING AND BE PATIENT TO NEAR THE END. Models could be having big troubles/errors here.
I hope to have a better handle on this by Wednesday AM, in giving a good shot at a New Years forecast. Driving and travel could be an issue Thursday night into Friday night, so stay tuned and I'll give it my best shot. Overall We'll most likely see Rain/Ice/and some snow with this possibly prolonged event from Thursday into the early part of the weekend.
For more discussion on this topic: Ruggie weather Forum