Thursday PM – Friday AM Event:
A weak area of low pressure will track off the NJ Coast, late Thursday night into Friday morning delivering a quick 1 – 3″ (iso. 4″) to our region. Snow intensity should be light – moderate at times that could make for a slippery commute Friday morning. This system will help setup a baroclinic zone (region in which a temperature gradient exists on a constant pressure surface ) for the much more significant system Saturday into Sunday.
Saturday PM – Sunday:
An area of low pressure system will develop over the Midwest tracking towards the East Coast, entering our region Saturday night into Sunday. Currently there is great amount of uncertainty regarding the track of the system once it enters our region, with modeling in disagreement with each other. The ECWMF (EURO), UKMET, and NAM models support a more south-easterly track off the NJ Coast with front-end heavy snow, turning over to a prolonged icing event, transitioning back to snow once the low pulls far enough east off the coast.
The GFS and Canadian models remain the outliers with a more northwesterly track causing the low to cut to our west with heavy front-end snow transitioning to rain. The “trend” over the past 24 hours has been the movement of the low pressure system more southeast putting us more on the cold side of the low pressure system. This is due to the modeling showing less interaction between the tropospheric polar vortex and the southern stream energy over the past 24 hours leading to a flatter flow on the East Coast. Therefore, my current thoughts lie mostly in-line with the 1st model camp. If the southeastern trend of the low continues, we could see an all snow event with no precipitation change over occurring. Another reason I favor the colder solution is due to the cold air damming due to a high pressure system that will build over Canada funneling cold air southward much like our system back in November (and we all know how that turned out). This is almost always under modeled up to the event, and can lead to surprises like higher snowfall totals. Too early to get into specific details like snowfall amounts and such but there will be a significant moisture fetch with this system, with upwards of 1.5 – 2″ of liquid equivalent so what ever falls from the atmosphere will be mostly moderate – heavy precipitation. Will be back with an update tomorrow.