I'm not that far north of you (just into NY), and it has been too late to put down winter fertilizer where I am for two weeks now. The best time is when the top growth has slowed dramatically but the soil is still warm. The ground is now frozen where I am.

The best alternative at this point? Think Spring...

Well agian I not that far northor raise cool season weeds, but there is a reason fertizers are not available in your area. Let it rest.

If your grass is still green and growing some you can still put down urea. (Obviously, if you're soil is frozen, its not likely green and growing). The time for a last shot of quick release nitrogen is just after its gets cold enough to stop topgrowth for the season.

That varies. If you haven't had that happen yet, put down 1 to 1 and quarter pounds of nitrogen per thousand square feet in the form of urea, ammonia sulfate, etc.

All gardening is local.

What they said above is right for average. In your zone,

http://www.growit.com/bin/USDAZoneMaps.exe?MyState=nj

you are on average probably past the time to do any more fertilizing. The question is, are you running a little late this year? From what I hear on TV, probably not.