Last year at this time New York was starting its second week of an extraordinary early-winter warm spell. No such luck this year as December has so far been averaging about five degrees below normal. Today will be our first warmer than average day in a week and only the third such day this month. We can expect a high around 45 degrees.
Both the Weather Service and the Weather Channel are predicting highs in the 40s for the forseeable future. Well, the Weather Channel has gone crazy with the cold on Friday but we're ignoring that one. No white Christmas for the Big Apple! We may see a bit of rain later today. The rain may mix with, or turn to, snow tomorrow. In neither case is the chance of precipitation all that great, and we don't expect much accumulation even if is rain or snow does occur.
The rain shouldn't amount to much today because the air near the ground is really dry. Look at the sky later this afternoon and you may see streaks of snow fall beneath the clouds. These fall streaks, falling snow that sublimates before reaching the ground, just can't survive very long in the dry air. If you were to fly through a fall streak you'd be in a fairly intense snow storm. The dissapating snow moistens the dry air below, which allows the snow to fall further before sublimating, which moistens the air even more, and so on until the air is humid enough that the snow reaches the ground. In today's case though it will be rain as it is warm enough for the snow to melt.
Current snow cover map from the National Operational Hydrological Remote Sensing Center, which has all sorts of nifty snow maps.