This FIRST GUESS is based on the 18Z operational (the regular GFS model) the 18z GFS ensembles, the 18z Operational European model and the 18z European ensembles. Unlike the last event, this one does not appear to be a rapidly changing or dramatically increasing event. There is not a lot of change from the 12z Global models to the 18z models.
Notice that there are two distinct areas of 4 to 7 inch snow bands. One is located in Kentucky and West Virginia and the other is in southeast New England For the time being, I have kept these 4 to 7 inch snow areas separated and do not connect them across the big cities of DC Baltimore Philly and New York City. That may change in further updates
Perhaps the most important change Is that there continues to be a slight shift south and east of the track of the developing surface LOW on Thursday night and Friday. This is occurring because of this particular image which shows a strong piece of energy in the northern Jetstream cutting across the Great Lakes on Wednesday afternoon evening. This piece of energy is being modeled stronger on the latest model runs.
This forces the next piece of energy that becomes the winter storm on Thursday night and Friday, to track a little further to the South. Without getting too technical, it is a basic rule in meteorology and in synoptic forecasting that you can’t have two pieces of energy (short waves) in the jet stream in close proximity to each other. In this particular case this rule means that the next piece of energy that comes out of the Rockies and the upper Plains is forced to drop a little further to the South.
This forces the surface LOW to a bit more to the south reduces the threat of significant snow in interior New England interior, interior southeast New York state and northeastern Pennsylvania. It also increases the chances of the mix precipitation in Central Virginia in and around areas such as Richmond changing over more rapidly to all snow.
The start time map is pretty self-explanatory. This is a fairly fast-moving system and the rapid speed of the system is going to keep the snow amounts down.
