[12Z NAM forecast map for early tomorrow evening showing precipitation associated with both clipper systems]
It has been quite an active period in the Mid-Atlantic region over the past week or so with three different accumulating snow events to deal with and now two separate clipper systems will bring more snow to the region on Tuesday and Tuesday night.
The first clipper will push snow into the I-95 corridor region after about 4 am or so and it will likely have an impact on the Tuesday morning rush hour in Philly and New York City and perhaps even as far south as the DC metro region where they will be on the southern edge of the precipitation shield. The snow will continue in Philly through the morning and a brand new 1-3 inches can accumulate by mid-day with the tendency for the higher amounts to be north of Philly. Snow will last into the early-to-mid afternoon hours across the New York City region where 2-4 inches can accumulate as the clipper intensifies somewhat upon reaching the still relatively warm waters of the Atlantic Ocean. Then there will be a break for several hours across the I-95 corridor with just cloudy, cold and dry conditions before the second clipper races into the region from the northwest.
The second clipper is likely to move slightly farther south than the first system giving the DC region, Delmarva Peninsula, and the southern part of New Jersey a better shot at small accumulations later tomorrow night. While the Philly region may very well get more snow shower activity later tomorrow night from this second clipper, it is possible the bulk of its snowfall stays south of New York City. One final note - the typical 10-to-1 ratio of snow-to-precipitable water (e.g., 1 inch of rain equals 10 inches of snow) may be on the low side for these two events; especially, for the system coming tomorrow night. Upper air temperatures will be quite cold and dropping on Tuesday so the snow-to-rain ratio may be more on the order of 15-to-1 or so. The result of this: a light, fluffy type of snowfall that sweeps away rather easily.