For watching such developments:

Interestingly, this might be just a tad further south than had been modeled.
Overall, this system should ride northeastward and then develop at an increasing rate as it moves through the waters off the Mid-Atlantic region. However, its track will likely be too far offshore to bring the major Metropolitan areas from Washington, DC to New York City the chance of a significant snowfall. Strong cold air advection from the north should also help create a sharp boundary between areas that receive accumulating snow and those that do not.
One should also expect that the push of Arctic air will probably be stronger than modeled. For example, here are select comparisons of 12z temperatures and those forecast by the MAV:
Chicago: 5° vs. Forecast: 8°
Detroit: 6° vs. Forecast: 16°
Toledo: 10° vs. Forecast: 18°
Overall, in terms of temperatures, I expect the following for select cities tomorrow:
Boston: Falling into the teens during the latter part of the morning
New York City: 16° during the morning
Philadelphia: 17° during the morning
Washington, DC: 20° during the morning
New York City’s afternoon temperature may reach no higher than 22° and Boston may stay in the teens during most or all of the afternoon. Wind chills will be harsh.
My final ideas on the snowfall, which represent generally small adjustments that assume somewhat of a deformation zone to develop across eastern Connecticut, Rhode Island, eastern Massachusetts, and possibly easternmost Long Island:
Boston: 3” – 6”
Cape Cod: 4” – 8”
Greenwich: Coating to 1”
Montauk Point: 1” – 3”
New Haven: 1” – 2”
New York City: Coating to 1”
Newark: Coating to 1”
Philadelphia: Coating
Providence: 3” – 6”
White Plains: Near 1”