On Monday, low pressure will pull out of the south-central states and head towards the Ohio Valley. A secondary low pressure system will begin to form late Monday night off the Mid-Atlantic coastline. The day will start off on the cold, dry side in the DC-to-Philly-to-NYC corridor as moisture begins to head in this direction from the west-to-southwest.
In the DC metro region, precipitation in the form of ice and/or rain is likely to arrive during the afternoon hours and then continue into Tuesday. The morning commute looks like it will be dry in the DC metro region. There is a chance that any ice or rain that falls can change to snow during the latter stages of the storm on Tuesday as the Mid-Atlantic coastal storm takes over and pulls colder air southeastward.
In areas to the north of the PA/MD border, the early week winter storm is likely to be primarily a snow and/or ice event with precipitation arriving by the end of the afternoon or early evening hours and continuing into Tuesday. The morning commute looks like it will be dry in the Philly and NYC metro regions. Accumulations of at least a few inches of snow are on the table from the Philly northern and western suburbs to upstate Pennsylvania and also to the New York City metro region.