Forecasters have growing confidence that it's going to snow tomorrow in the Mid-Atlantic and Northeast. Some cities from Pennsylvania to Long Island could see five or more inches of snow by the time it's over on Friday night. Oh, and tomorrow is the first day of spring. Nature has a twisted sense of humor.

March is notorious for its strange and constantly changing weather. You could need shorts, a jacket, a snow shovel, and an umbrella all in the course of a few days. Just look at Washington D.C., where it was 73°F on Tuesday, it could snow tomorrow, and then they're predicting temperatures back in the 60s by Saturday.

So, what's going on? A weak area of low pressure moving towards the Northeast is making for a dreary afternoon from North Carolina west through the Ohio Valley. This rain will move into the Mid-Atlantic tonight and start to interact with cold air over the area, slowly changing the precipitation over to snow from north to south as the system pushes farther into the area through the day on Friday.

Moderate to heavy snow will start to fall from Pennsylvania to southeastern New England during the afternoon and evening on Friday, with the worst snow accumulating around the Interstate 95 corridor just in time for the evening rush hour.

Here's a look at the National Weather Service's forecast snow totals from their 4:00 PM EDT update:

The heaviest snow will probably fall from the Appalachian Mountains in southern Pennsylvania east through New Jersey and Long Island. Snowfall accumulations could reach six inches under the heaviest bands of snow, and New York City stands to see the most snow of the major cities affected (around five inches).

Keeping in mind the fact that we do not name winter storms in the United States, The Weather Channel's forecast is pretty close to the one issued by NWS offices above, showing the heaviest snow falling across parts of Pennsylvania, New Jersey, and Long Island.

The track of the storm and the temperature profile of the atmosphere could shift the location of the rain/snow line and affect who sees how much snow. As always, the forecasts can and will change through the overnight hours and into the day tomorrow. Many marginal snow events like this come down to nowcasting—predicting who will see what based on observed temperatures. If temperatures are warmer going into the event than the models are showing right now, you can forget a decent snow event.

Prepare for the worst case scenario (shovelable snow) but hope for the best (a cold, dreary rain).

Snow on the first day of spring is a cruel slap in the face after the colder-than-normal winter we've seen in much of the eastern United States, but it's not unprecedented. The average last day with measurable snow at Washington National is March 3; the magic date is March 14 in Philly, March 19 (today!) at New York City's Central Park, and March 30 in Boston. For the record, it can still snow well into April—the latest snow on record at Central Park was April 27, 1967, when a dusting of snow fell.

Stay safe, and enjoy what could be (hopefully will be) the last decent snow event of the year.

[Images: GREarth, NWS, The Weather Channel]

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