Light snow fell throughout much of the area for the first time in a few weeks, in the midst of a winter that has offered less than 10 inches of snow so far throughout the majority of the forecast area. It has been a transitional winter for sure -- with temperatures soaring into the 50's only to be followed a few days later by some light snow, and then another warm up. However, the end of this week into this weekend looks to offer something at least slightly different as a somewhat wintry pattern will continue for more than two or three days. Behind the light-snow producing storm system on Wednesday, an average airmass will build into the forecast area for Thursday and Friday, with highs in the mid 40's. However, Polar air will be lurking to our north on Friday...and as energy from the southern stream of the jet phases with a piece of the Polar Vortex, a storm forming well offshore could touch off some moderate precipitation over our area. The main storm won't form until it's well north of our area -- but there still could be a light snow throughout much of the area as it swings by. Pictured right: NAM model showing light snow impacting our area Saturday afternoon.

The details are still being ironed out by most of the forecast guidance, but the general idea is that a piece of the Polar Vortex will drop southward towards New England. At the same time, a piece of energy to the southwest of our area will move north and east, and eventually phase with the Polar Vortex in the Northwest Atlantic. The graphic to the left shows this development, as we can see the three stages of the phase in the middle of the atmosphere (at 500mb). We put a yellow dot over New York City as a point of reference.  In the first image on the far left, the southern stream energy over the Southeast states is moving north and east, which a broad piece of northern stream energy in relation to the Polar Vortex is moving east/southeast. We can see them begin to interact in the second frame (in the middle), and finally the phase occurs on the frame to the far right.

As the phase occurs, a strong surface low will develop over the Northwest Atlantic. At this point, some very heavy precipitation will develop near and to the north and west of the surface low. Fortunately for us, this will be after the system has passed our region. However, the forecast models are still showing a swath of light to moderate precipitation as the system passes by during the beginning stages of the phase.  We can see that in the image to the right, from the GFS model's depiction of the system. On the left side we can see the 6 hr precipitation valid Saturday afternoon, showing generally light to moderate precipitation over our area and heavier precipitation offshore. To the right, we can see the GFS forecast surface pressure...which shows the surface low well out over the Atlantic Ocean.

Essentially, the potential does exist for some light to moderate snow over our area Friday Night into Saturday as the storm organizes. That being said, the potential for a moderate impact event is very low...as the storm system is forecast by all guidance to develop very far away from our area. Still, we could see some light accumulations throughout most of the area if the forecast models are correct. Uncertainty is still very high -- so stay tuned! There is still the potential for things to change dramatically

Finally, as the system phases, the Polar Vortex is pulled southward over New England later Saturday into Sunday. This will bring a shot of Polar Air to the entire area -- likely meaning one of the colder nights/days of the winter the second half of this weekend.