Winter has officially kicked off this week with an Arctic blast followed by a flurry of e-mail concerning the potential winter storm for this weekend. As usual, the computer models offer varying solutions representing everything from a major snowstorm to a mix of snow and rain to a small nuisance for New York City.

Like with many East Coast winter weather events, the key factor is a bubble of cold air over Quebec and how far it spills south. It has to spread far enough south so the air remains cold enough to offset any onshore winds (water temperatures off NYC are around 50 degrees), but be forgiving enough to allow moisture to encroach from the south into our area.

What seems most likely is a sharp cutoff in precipitation somewhere over New York and New England. Dry, cold air will dive south tomorrow night from north of Montreal while more humid air is lifted north from the Virginia/North Carolina coast. Even a small error in terms of distance may result in a blown forecast with large errors in terms of inches of snow.