2:45 PM | **The threat remains for accumulating snow in the Mid-Atlantic region later Sunday into Monday - but stay tuned**
Overview While chances do remain for accumulating snow in much of the Mid-Atlantic from late Sunday into Monday, there is nothing certain at this time and a small shift can mean a big difference. After a relatively mild day on Saturday, colder air will push into the Mid-Atlantic region from the northwest on Saturday night and Sunday. This injection of fresh Arctic air will be anchored by strong high pressure that will be edging into southeastern Canada later Sunday into Monday – a good location for holding cold air in the Mid-Atlantic region and a crucial player in this upcoming threat for accumulating snow. At the same time, an area of low pressure - supported by a couple pieces of energy in the upper atmosphere - will organize in the Southeast US and it will head northeastward towards the Mid-Atlantic region with plenty of moisture to “overrun” the dense, cold Arctic air mass. One important question that still remains at this time is “exactly how far to the north and east in the Mid-Atlantic region can the moist air advance as it encounters this fresh cold, dense and dry Arctic air mass”. Right now, it appears that there is a greater chance for significant snow to the south and west in the Mid-Atlantic region (e.g., from DC to the South Jersey Shore) and less to the north and east (e.g., NYC metro region); Philly is certainly still in the ball park.
Details Precipitation is likely to break out in the DC metro region during the mid-to-late afternoon hours on Sunday and then perhaps in Philly a few hours later. The precipitation may start as rain in the DC metro region before changing over to snow, but would likely begin as snow in the Philly metro region. Snow may then continue into early Monday in the DC metro region - and perhaps as far north and east as Philly - and while there can be a mixture at times with sleet and/or freezing rain, snow accumulations are likely by Monday morning. At this time, the New York City metro region appears to be on the northern fringes of the precipitation field for this upcoming event and it is definitely too early to make any kind of a confident call for accumulating snow up there.
General notes Snow accumulations this late in the winter season are sometimes largely dependent on “altitude” and “time of day” in that snow has a much better shot at sticking on the ground during nighttime hours and at higher elevation locations which will tend to accumulate much quicker than lower spots in marginally cold situations this time of year. One other note, Philly Airport needs only 2.6” of snow to match the 2nd snowiest winter ever of 1995-1996 (65.5”) and it is 15.8” behind the snowiest winter ever of 2009-2010 (78.7”)…just saying.
Stay tuned to “thesiweather.com” this weekend for updates noting that there is still quite some time to go before this potential storm reaches our area and a small swing to the south or north can make a big difference.