A significant winter storm will impact portions of the I-95 corridor on Sunday; however, it appears the earlier forecast storm track has shifted a bit, which means more snow for more people across the northeast. After the storm exits the coast, dangerously cold weather will pour over much of the eastern and southern United States.
An Arctic cold front is responsible for this wintry weather; early Sunday that front will be moving in from the north and west and head to the Mid Atlantic coast where it will stall. This frontal boundary will stretch all the way down into the southeastern states and it is along the boundary that there will be a developing low pressure system located over the Carolinas early Sunday morning. Meanwhile, there will be energy aloft rounding the base of a large and deep long wave trough setting up over the central and eastern continental U.S. . As this energy aloft interacts with the front and developing low, low pressure will move north and east through the day Sunday while it deepens.
At this time, it appears the storm will track a bit closer to the coast than earlier expected and cross through southeastern New England. Because of this shift, the heaviest snow will fall to the north and west of the I-95 corridor between Philadelphia and New York and across interior southeastern New England and Maine. In extreme southeastern New England including Cape Cod, far eastern Long Island, and much of the Jersey Shore, the storm center will be too close to allow for a great amount of cold air to enter those places; as a result, rain or a wintry mix of sleet, rain, and snow will fall, keeping snow accumulations lower than initially expected.
In terms of timing in the Mid Atlantic, expect the precipitation to move in southwest to northeast beginning by mid to late morning Sunday with the heaviest falling during the afternoon into the early evening. In the areas that see all snow such as Berks County into the Lehigh Valley north and northeast through the southern Poconos and northwestern New Jersey, snowfall rates could exceed 1″/hour Sunday afternoon as the surface low deepens to the east. Near the I-95 corridor, with temperatures right around if not just above freezing as the precipitation begins, it may actually start as rain before turning over to snow as dynamic and evaporational cooling effects take hold. Then, as the low tracks up the coast through the day, a mix with or change back to rain or sleet may occur in the afternoon for a time before any mixing flips back to snow before ending Sunday evening. South of there, mainly rain and mixed precipitation is favored. Should the storm track just a few miles east/west from where it is expected to now, there could be significant changes to the forecast: a shift west would push heavier snow more west and more rain closer to the I-95 corridor while a shift more east could drag cold air to the coast, leading to heavier snowfall amounts along the I-95 corridor and points east.
As Artic air blows across the Great Lakes, significant lake effect snow is also expected across portions of Michigan and New York.
In wake of the system on Sunday night, the beginning of the cold air mass will take aim at the Mid Atlantic. Skies will begin to gradually clear late Sunday night into Monday morning, and with a fresh snowpack in place, this should result in low temperatures falling into the single digits and teens for many locations. With a stiff northwest wind filling in on the backside of the departing low, wind chills will drop into the single digits for most.
Dangerously cold weather will arrive later Monday, posing risks for both people and animals. With bitter cold air arriving, there will be an increased risk of hypothermia and frost bite for living things and threats to infrastructure such as freezing water pipes and high demand for heating energy.
