A strong shortwave diving through the eastern Great Lakes on Monday morning was absorbed by a stronger upper-level low-pressure system located in the Canadian Maritimes. As the southern shortwave was being absorbed, strong divergence and diffluence shifted towards the New Jersey coastal waters. As a result, a new low-pressure system began to develop in the New Jersey coastal waters, to the south of central Long Island. This process created a stretching in the atmosphere and the formation of an inverted trough from central New Jersey through northeastern Pennsylvania.
The strong concentration of diffluence and divergence along and north of the trough along with moisture transport from the Atlantic Ocean supported an area of moderate to heavy precipitation. Precipitation types varied due to boundary layer and mid-layer temperature fields. At 850 MB, the entire Northern Mid-Atlantic was below freezing. However, due to the eastern fetch between the collapsing low-pressure system and the new one, temperatures were above freezing at 925 MB from northern New Jersey through the New York City metropolitan area and central New Jersey, and at the surface temperatures were above freezing on the immediate coast. As a result, snow with a ratio of 8:1 to 12:1 was found in the higher elevations where snowfall totals exceed 2″ while a mix of sleet and rain was found in the northwestern suburbs of New York City and a rain/snow mix on the coast.
The low-pressure system and trough exited the region by early Monday morning with precipitation ending by 6 AM.
The forecast was verified by 99% in terms of amounts but ended 2 hours earlier than expected.
