Zone 3/7 (Interior) Update: Wintry weather expected on Monday

A Nor’Easter as unique as it will be strong is expected to develop throughout the Eastern United States on Monday. The storm is already in its developmental stages well to our south, and will shift northward into the Mid Atlantic states through Monday morning. A surface low pressure area is expected to then redevelop off the coast, strengthening near the Delmarva and then shifting eastwards towards the 40/70 Benchmark.

All of these things would bring one to believe a winter storm is on the way. Think again! A warm, modified, Pacific airmass is in place prior to the storms arrival (have you been outside recently?) and the main focus of the storm will be torrential rain and wind near the coasts. However, the storms dynamics and cold air aloft will work to create wintry possibilities inland, even despite the warm air at the surface to start.

Very cold air exists a few thousand feet above our heads on Monday, with the storm system drawing in even colder air as it strengthens nearby on Monday. With a low pressure developing off the coast, bands of very heavy precipitation are expected to rotate inland from the Atlantic Ocean. As precipitation begins to increase in intensity, the process of dynamic cooling will begin.

Simulated radar through Monday evening. Notice sleet and freezing rain in higher elevations and interior.

Simulated radar through Monday evening. Notice sleet and freezing rain in higher elevations and interior.

This occurs when the rate of precipitation acts to cool the environment around it in the atmosphere. With cold air present a few thousand feet up, and heavy precipitation falling — acting to cool the environment further — forecast models have begun to catch on to the idea that wintry precipitation could fall in the interior and higher elevations.

This precipitation is most likely to fall in the form of sleet. Why? Snow flakes that form well above our heads will melt on the way down. But the rate of precipitation will actually allow them to refreeze as they fall quickly through colder layers of the atmosphere and then to the surface. The result? Ice pellets, more affectionately known as sleet.

This potential will be maximized, as mentioned, inland and in the higher elevations. Sleet may be particularly prevalent in areas like far Northwest NJ, Southeast NY, and interior CT. The wintry weather threat may even seep a little further southeast of there, towards the Ramapo Mountains of NJ and into places like Putnam County in New York.

Local winter impact weather expectations through Monday evening.

Local winter impact weather expectations through Monday evening.

Southeast of those areas, the transition should be marked — with only rain likely throughout much of Southeast Passaic, Bergen, and Westchester Counties. These areas will mark a transition area, where strong winds and torrential rain will become a bigger story, especially as one heads further towards the coast.

Sleet accumulations are likely to range from 1-2″ in the interior and higher elevations, to T-1″ in the further southeast areas. Locations away from the interior and closer to the coast will not see much wintry precipitation at all. We’ve included an impact map below with details on wintry weather expectations on Monday through Monday evening. Further updates are likely Monday morning as new data is available!