Details are slowly coming together for a likely east coast snow storm this coming weekend. While the odds of a storm somewhere along the east coast has increased over the last 24 hours, details of where the snow will set-up and where the rain/snow line will be remain sketchy at best. Important atmospheric data will be sampled tomorrow, helping meteorologists and some of the computer forecast guidance they use in forecasting to improve the overall understanding of a fairly complex weather pattern.
Before we get to the “main event” on Sunday, we need to deal with a fast-moving, weaker system later Thursday and Friday. A weak low pressure system originating in Canada, commonly referred to as a “clipper system”, will approach the Mid Atlantic Thursday night and exit the northeast on Friday. This system will have limited cold air and moisture to work with; as a result, precipitation will be light, and for many it’ll be in liquid form. North of I-195 and south of I-80 in New Jersey, west through Pennsylvania between I-80 and I-276/76, an inch or two of snow may fall by Friday evening, with upwards of 3″ possible in the higher terrain of central Pennsylvania. South of this area, mainly light rain is possible which could end briefly as a period of wet snow with little to no accumulations.
More importantly, this clipper system will help usher in a significantly colder air mass into the eastern US to close out the week and chill down the weekend.
Cold high pressure looks to be in place on Saturday with highs generally 10-15 degrees below normal across much of the Northeast and Mid Atlantic. The potency of this cold high pressure system and the general atmospheric flow across the continent will help determine what exactly happens on Sunday with the potential east coast snow storm.
A few days ago, the European ECMWF forecast model was calling for an all-out blizzard for portions of the eastern United States –a solution we quickly discounted. But it along with other guidance, such as the American GFS forecast model, has come around with more reasonable solutions. While not a blizzard by any means, a significant snowfall is very possible.
There are two possible scenarios for this Sunday storm.
One possibility is the cold high pressure system moving in on Saturday will help supress Sunday’s storm system to the south. Similar to a scenario that happened in January, this could bring heavy snow to portions of Virginia, especially the Hampton Roads / Virginia Beach region. Snow totals will drastically drop off to the north in this scenario, with Cape May, New Jersey on the northern fringe of accumulating snow. This scenario is supported by the latest overnight guidance from both the European ECMWF and American GFS forecast models.
The other scenario suggests that the cold high pressure system won’t be as strong; this would allow the storm system on Sunday to move closer up the northeast coast. This would shift the axis of heavier precipitation further north, but it would also bring the rain/snow line further north too. If such a scenario were to unfold, Pennsylvania and New Jersey would see the heaviest snow, with accumulating snow reaching north along the I-95 corridor, perhaps as far north as Boston. The rain/snow line would flirt with the Pennsylvania/Maryland border and southern New Jersey, keeping any snow totals in those areas low.
Until more of that atmospheric data is sampled, it is still too early to say which scenario will unfold. It is also too early to say which forecast model is “right” or “wrong”, especially with that data not yet ingested by the models. More data will come in over the next 24-48 hours which will help us improve the weekend forecast.
To recap:
- A relatively weak clipper system will bring light precipitation to portions of the northern Mid Atlantic later Thursday into Friday.
- This clipper system will help usher in a much colder air mass into the northeast.
- Depending how strong that high is and how strong a low will be to its south will be, a snow storm is likely somewhere along the east coast; it is just too soon to say where that accumulating snow will set-up.
- Forecast guidance is suggesting now that best chances for the heaviest, accumulating snow will be in southeastern Virginia. But until additional data comes in, such guidance can’t be treated as gospel.
- Additional data will be in over the next 24-48 hours, which will help meteorologists solidify the weekend forecast.
