It is a nipping and an eager air.
Horatio's observation came to mind this evening: the air seems much colder than the mid 30s and seems to portend wintry doom.
So what can we expect from this storm?
Temperatures are dropping rapidly, so most of what we'll see will be snow.
(Note: forecast area for this storm includes Lehigh Valley, Berks, Montco, Chester, Bucks, and central/north Jersey. Lancaster, Philly, south Jersey and Delaware will see more mixing and less snow.)
Light snow begins 2-3am and becomes steady for the morning commute. Snow will stick to roads, particularly as surface temperatures remain below freezing and the sun has yet to rise.
Snow mixes with (and briefly changes to) rain in the afternoon as temperatures rise above freezing, then ends as snow in the early evening. Steadiest period of snow will be roughly 6am-12noon. This is a fast-moving storm, so the it will ... well, it will move right on through.
Accumulations: an inch or two generally. We could see a bit more with banding, especially in the higher elevations. Indications are that some areas could see as much as 3-5 inches--but most places, just an inch or two. (Philly and the other areas mentioned get just a coating to an inch of slushy precipitation.)
Delays/cancellations: Considering the two or three (or much more, in Jersey) days we had off for Sandy, I don't see administrators burning a snow day for this pittance. Delay isn't out of the question, since the roads should be less treacherous after sunrise (a couple of minutes after 7am).
Chance of cancellation: 15%
Chance of delay: 35%
Chance of early dismissal Tuesday: 10%
So there you have it.