A significant storm system will approach the area later Wednesday evening, as a disturbance in the mid levels of the atmosphere shifts from the Central United States to the Mid-Atlantic coast just south of the area. At the surface, a frontal boundary near the area will shift near the area by later Wednesday morning and afternoon. This frontal boundary will bring scattered showers and mostly cloudy conditions to the area on Wednesday, and as it approaches the area temperatures will actually gradually fall throughout the day on Wednesday. High temperatures could be observed fairly early in the day. However, the frontal boundary will be a much more important factor beginning Wednesday night. With the strong mid level disturbance approaching and interacting with the front, the front itself will serve as a focal point for the development of heavy precipitation Wednesday Night into Thursday morning. It will also dictate roughly where the "gradient" will begin to develop between the heavy rain and rain and snow mix. Pictured right: NAM model's simulated radar imagery showing a period of moderate snowfall over New Jersey Thursday morning before the system exits the area.

This provides a major headache in the forecast -- as the changeover becomes extremely unpredictable. We've seen these before, most recently (and noteably) this past October 29th. The changeover area can depend on several things, including the intensity of the precipitation, the degree of cold air at different levels of the atmosphere, and the exact track of the storm. This storm will likely bring uncertanties regarding all of those right down to the final hours of it's occurance. In situations like this, it is prudent to first lay out the things which we know are on the table and likely won't change. First, we know that the airmass in place before the storm is very poor for frozen precipitation, especially with the front approaching the area and warm temperatures ahead of it. Second, we know that the system is forecast to be very intense, which could lead to some very impressive dynamics. Finally, we know that this system will be a significant rain producer throughout the entire area regardless of how much snow falls at the back end. Forecast models are indicative of the potential for near 2 inches of rain.

At this point, the chances of getting accumulating snow along the coast are very low. The lack of cold air in place prior to the system means that the system has to dynamically cool the atmosphere to realize the cold air potential which is working into the system gradually. Near the coast, this process will take longer to occur. By the time it does, most of the steady precipitation should be over. Further inland, concerns remain in regards to the exact timing of the changeover, the snowflake quality (bad snowflakes can seriously hinder snowfall rates and accumulations) and the storm track. Currently, our forecast calls for little to no snow accumulation along the coast and in New York City. To the west of the city, a slushy trace to an inch of snow may fall as the storm pulls away. These areas could recieve an hour or so of moderate snow. Much farther inland, across the higher elevations of Northwest New Jersey, Southeast New York, and Western Connecticut, the potential exists for 2 to 5 inches of snow with potentially higher amounts in isolated areas. Pictured left: Our latest storm total snowfall forecast, valid through 2:00pm Thursday December 8th, 2011

The storm is expected to wrap up by Thursday afternoon with precipitation ending from west to east. We encourage you to stay with us over the next 24+ hours as the storm system draws near. We'll be updating constantly with new forecast maps and information as soon as we get it. Note that the below forecast is for New York City only. The forecast for the entire area will be posted within the next hour (link will be posted on Facebook & Twitter accounts).

Wednesday: Cloudy with showers likely. High near 55.  North winds around 10 miles per hour. New rainfall of 0.10" to 0.20" possible.


Wednesday Night: Mostly cloudy, with rain likely, possibly mixing with a few snow flakes late. Overnight low near 37. North wind near 10 miles per hour.  Chance of precipitation is 70%. New rainfall of 0.25" to 0.50" possible. No new snowfall accumulation expected.

Thursday: Cloudy with rain likely, possibly changing to a brief period of snow and then dissipating from west to east. High near 46.  West winds around 15 to 25 miles per hour. No new snowfall accumulation expected.

Thursday Night: Partly cloudy and breezy, with a low around 33. West winds around 15 to 25 miles per hour.

 Article written by JH. Published December 7th, 2011 at 12:00am. Looking for a forecast? Use our new Forecast Beta tool to see the latest forecast in your specific area for the upcoming week, or view our Technical Forecast Discussion for the more serious weather enthusiasts. Also, check out our new Forecast Overview tab. For up to the minute details on forecasts, watches, warnings, and alerts, follow us on Twitter and Facebook.