New York City will get a foot of snow according to the NWS. Now that European and American weather models are coming into better agreement the forecast of a major winter storm on Friday and Saturday for New York and New England is coming into clearer focus with much of southern New England forecast to get about 2 feet of snow.
The storm that has just reached the coastal Carolinas will blow up as it hits the Gulf Stream off of Cape Hatteras. A wave in the jet stream now over the mid west will pull in cold air aloft towards the developing coastal storm, destabilizing the atmosphere. Extremely rapid intensification will happen as the storm tracks over warm Gulf Stream waters.
The blue colors indicate below freezing air at the 850mb level that tends to control whether it's rain or snow. This model run keeps the rain out to sea. It forecasts very heavy snow this Saturday morning in New England.
The northern wall of the Gulf Stream along the east coast began expanding northward in the mid 1990s. Meanwhile, this winter the polar vortex split in two and one vortex pushed south towards eastern Canada. The extreme interactions between the warm North Atlantic waters and the cold Arctic air pushed south have caused a series of extremely intense storms in the North Atlantic ocean. The previous storms didn't impact the east coast of the U.S.
Much warmer than normal water along the storm's track will contribute to its rapid intensification and high precipitation amounts. Water temperatures 9 degrees F above normal will provide an additional jolt of water vapor to the storm.
The east coast has been pounded by heavier snows over the past 20 years because of the increase in moisture from the Gulf Stream.