The Middle Atlantic region enjoyed a preview of spring today with highs in the 50s and even some 60s across Baltimore and Washington. After a chilly day on Sunday, mild air returns to the area on Monday and Tuesday with highs once again in the 50s with some isolated spots in the lower 60s. As is typical this time of year, warm-ups are often short-lived and by later next week there are indications that a storm system may threaten the northeast United States with another round of wintry precipitation in the form of snow, sleet, and rain.
Low pressure will develop over the plains states and move east, probably moving just to the south of Washington and Baltimore near the mouth of Chesapeake Bay early Thursday. The area of low pressure will be rather weak until it reaches the coast when it will deepen and strengthen into a more powerful storm. At this time, precipitation looks to fall in the form of rain for Baltimore and Washington. Philadelphia may begin with mixed precipitation that changes over to rain. As the storm strengthens and pulls in colder air in its wake, precipitation may end as snow in Philadelphia, Baltimore, and Washington. Of the three locations, Philadelphia has the best chance for accumulating snow.
One of the ingredients that is necessary for a significant snowfall in the Middle Atlantic region is a strong area of cold high pressure to the north. There will be an area of high pressure in southern Canada, but this high will be located over the province of Ontario. Ideally, the center of high pressure should be located in Quebec or Maine in order to provide a source of fresh cold air for the storm to tap into. With marginally cold temperatures in the Mid-Atlantic states, and with the storm moving too close to the cities of Washington, Baltimore, and Philadelphia; this system looks to be more wet than white. Generally speaking, storms that move north of Norfolk VA bring in enough mild air to cause precipitation to fall as mixed rain or snow, or just plain rain. In summary, the four main factors that will likely prevent this from becoming a snowstorm in the Middle Atlantic states include the low coming too close to the cities, the center of high pressure in a less-than-favorable location, the weak nature of the storm (until it reaches the coast), and the higher impact of the March sun angle. Should any of these factors change in the coming days, we may need to reassess the forecast for Philadelphia, Baltimore, and Washington.
In the meantime, here are some links with more specific forecasts for your location:
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