11:00 AM | **Main action of the upcoming winter storm holds off until after dark...snow, sleet, freezing rain, and plain rain coming to the Mid-Atlantic region with amounts dependent on location**

[GOES water vapor image with lots of moisture headed our way from the Midwest/Central Plains]

Discussion

Overview A ton of moisture is headed to the Mid-Atlantic region and with temperatures near or below the freezing mark in many areas there can be a significant buildup of ice later tonight after some initial snowfall at the onset. The low pressure center will move from southern Indiana today to southwestern Pennsylvania by tomorrow morning at which time it will then tend to reform off of the New Jersey coastline. Warmer air at many levels of the atmosphere will advance northward into southern and central Pennsylvania during this storm, but eventually this northward movement will grind to a halt due to a developing blocking pattern over Greenland and the NW Atlantic Ocean and that is where a battle will take place.

North of the PA/MD border There is the chance for some snow later this afternoon in SE PA, NJ and NYC, but the main action begins later this evening. Given the current storm track, warmer air at upper levels of the atmosphere will advance as far north as central Pennsylvania and this will allow for any initial snow to mix with or change over to sleet and freezing rain later tonight where a buildup of ice can occur in the overnight hours. By tomorrow morning, temperatures could edge above freezing in southern sections of the Philly metro region, but they’ll be hard-pressed to rise above the freezing mark in the northern half of the region and in areas north and east of there (e.g., Lehigh Valley, NYC). An influx of colder air on the back end of the storm could bring a changeover of the precipitation back to all snow later Monday.

South of the PA/MD border While there can be snow later today in areas near the DC metro region, the main action begins later this evening with some snow at the onset or a mix of snow, sleet and freezing rain. As warmer air advances northward later tonight, temperatures will rise above freezing and the precipitation will change to plain rain except for perhaps some sections near the PA/MD border where icing may linger for a little longer. As a result, the region extending from DC to southern New Jersey will likely see minimal accumulations of snow and ice, but there can be some slippery spots during the first part of the storm late today or during the evening hours. Winds will pick up quite a bit later Monday as the storm pulls away to the northeast and intensifies.

Current estimates for this complicated forecast are as follows (storm timetable from late today to late Monday):

DC metro region: a coating to 2 inches of snow and ice; snow changes to sleet, freezing rain and then to plain rain by Monday morning

Southern New Jersey: a coating to 2 inches of snow and ice; snow changes to sleet, freezing rain and then to plain rain by Monday morning

Southern half of Philly metro region (includes Philly, Delaware County, Chester County, Lower Montgomery County, Lower Bucks County): 1-3 inches of snow and ice; snow changes to sleet and freezing rain, possibly even to plain rain for by early Monday; there can be some buildup of ice in the overnight hours, precipitation could then change back to all snow later Monday with back end snow accumulations possible

Northern half of Philly metro region (includes Upper Montgomery County, Upper Bucks County): 3-5 inches of snow and ice; snow changes to sleet and freezing rain with a significant buildup of ice possible in the overnight hours; temperatures will be hard-pressed to rise above the freezing mark by early tomorrow morning; precipitation could then change back to all snow later Monday with back end snow accumulations possible

NYC metro region: 4-8 inches of snow and ice; snow changes to sleet and freezing rain, some buildup of ice, temperatures will be hard-pressed to rise above freezing; precipitation could end as all snow on Monday with back end snow accumulations possible

N and W suburbs of NYC: 6-10 inches of snow and ice; snow mixes with sleet, some buildup of ice possible, should end as all snow on Monday with back end snow accumulations possible

No matter what happens with this storm regarding snowfall amounts, bitter cold air will follow the storm and then there will be another Arctic blast at the end of the week.