[Tuesday morning 12Z GFS 500 mb forecast map, circled area shows upper level short wave; map courtesy NOAA]
Arctic air will blast into the Mid-Atlantic region on Tuesday and it looks like it will be accompanied by some snow as low pressure forms near the Mid-Atlantic coastline along a frontal boundary zone. The latest computer forecast models (Euro, GFS and NAM) are now in general agreement that there will be some precipitation produced in the Mid-Atlantic region as a short wave in the upper atmosphere approaches the region at the same time Arctic air floods the region. Currently, the models do not suggest that there will be anything significant in terms of snowfall as their moisture depiction is rather limited; however, the dynamics in the upper atmosphere is quite impressive as a strong short wave rides through the southeastern part of a longer wave upper level trough. Often, when the upper level dynamics is this impressive-looking and capable of producing significant upward motion, increased moisture content will soon follow in the forecast models. As a result, this situation bears watching and snow accumulations are increasingly likely on Tuesday from DC-to-Philly-to-NYC. Brutal cold will take over Tuesday night with single digit temperatures and the bitter cold will be reinforced on Thursday night giving the Mid-Atlantic region quite a sustained cold stretch. In fact, another bitter cold Arctic air outbreak is destined to reach the northeast US early next week to continue the very cold weather pattern across the region.