The National Weather Service has now extended "Winter Storm Watches" into portions of Bucks and Montgomery Counties. The storm that will move into the Mid-Atlantic region on Wednesday is now causing accumulating snow across Wisconsin, Indiana and Illinois after dumping up to 18 inches across parts of North Dakota and a foot of snowfall in upstate Minnesota. Precipitation is likely to reach the Philly metro region late tonight in the form of rain, snow or a mixture of the two. As the day progresses on Wednesday, colder air will cause a changeover of the precipitation to primarily snow with the best chance for accumulations coming in the afternoon and evening hours. By tomorrow night, there should be all snow falling and total accumulations on the order of 3-6 inches are likely by the late evening hours with the higher amounts in that range generally to the south and west of Philly and the lower amounts generally to the north and east (ie for example, more snow in West Grove, Chester County compared to Pottstown, Montgomery County).
Elsewhere, even more snow is likely for the DC region with 6-12 inches possible by tomorrow night with the higher amounts in that range to the western side of the District. The “bullseye” region for snowfall amounts will likely end up being the higher elevation spots of eastern West Virginia, western Virginia and western Maryland where more than a foot can accumulate. Meanwhile, farther north and east, the New York City metro region is likely to receive less total precipitation from this storm compared to DC and Philly with snow accumulations of 1-3 inches possible there by Thursday morning. At the Jersey Shore, there will be rain pretty much all day tomorrow, but even there it should change to accumulating snow tomorrow night with 2-4 inches possible by Thursday morning. Also, the Jersey Shore will get 50+ mph winds and coastal flooding at times of high tide from late tomorrow into Thursday.
Stay tuned, March storms are often tricky and this is a low confidence forecast.