The threat continues for a period of ice and/or snow on Sunday in much of the Mid-Atlantic region before a likely changeover to plain rain. Strong high pressure will set up shop to our north by Sunday morning and it will anchor a cold, dense Arctic air mass that will have no trouble advancing southward on the eastern side of the Appalachian Mountains and into the big cities from DC to NYC. This classic “cold air damming” setup often leads to icing around here, at least for a several hour period, as milder, moist air is initially forced aloft on top of the cold, dense surface air. The 12Z GFS model run suggests that while the surface freezing line will be way down across southeastern Virginia come Sunday morning, above freezing air will already be working its way to the north in the upper part of the atmosphere. This potential setup will likely lead to a several hour period of frozen precipitation in much of the region in the form of sleet, freezing rain and/or snow before the milder air finally wins out and changes the precipitation to plain rain – at least from I-95 to the coast. Surface cold air will hang on even longer across places like central and northeastern Pennsylvania and an extended ice storm is a real threat in those areas. One final note, there has been a slight trend towards a colder and colder solution for this upcoming event and we’ll continue to monitor that over the next few days.