We’re tracking the threat for more snow from the Mid-Atlantic through New England this week as not one but two different coastal storms develop. This remains a highly-uncertain forecast, especially in New England, based on how we are still forecasting several days out in time and how there are still changes in the model guidance from run-to-run.
Our first storm will be a Colorado Low, originating from the leeward side of the Colorado Rockies. This storm will track eastward toward the Mid-Atlantic coast, while bringing severe weather to the Southeast on Monday. By Tuesday, this storm will move offshore and strengthen a bit further to a sub-1000 millibar low. This is not a strong storm and it will not become a “bomb cyclone.” This storm is tracking ahead of an incoming trough of low pressure, so this storm will likely head out to sea instead of moving up the coast and rapidly-strengthening toward New England. There is still time for shifts in the track of this low, however.
For now, the impacts from this storm will occur on Tuesday in the Mid-Atlantic region. A light to moderate snow is currently forecast at and near the Mason-Dixon Line from eastern West Virginia, through southern Pennsylvania, much of New Jersey, northern Virginia, Maryland, and Delaware. So that’s where snow is possible, but whether these areas deal with accumulating snow is the big question. Temperatures will be very marginal with most areas being in the mid 30s. Snowfall rates will also be light, so this wet snow may have a tough time accumulating while trying to overcome these marginal temperatures. The higher sun angle warming the ground will also be a limiting factor. Therefore, up to an inch of snow can be expected for most of these areas. There is the chance more than an inch falls and maybe closer to half a foot based on some of the ensemble guidance. Once you get into the higher elevations of western Maryland and eastern West Virginia where temperatures will be right around freezing, up to four inches of snow is possible. This is where all surfaces may deal with accumulations. By Tuesday evening, our storm will pull out to sea while our second storm begins to form over the southern Appalachians. Again, the track of this first storm is still not entirely set in stone. If it happens to track a bit more toward the north, then snow may fall in the New York City area, on Long Island, and the southern shore of New England. Either way, little to no snow accumulation is expected.
On the heels of the first storm is a second storm that will develop over the southern Appalachians under a trough of low pressure. The outcome of this storm is more uncertain than the first. This is because we are looking farther out in time and because the atmospheric dynamics associated with this storm is much more complicated. This storm will be stronger and has the potential to rapidly-intensify off the Carolina coast beginning Tuesday night. Based on the most recent guidance, the trend has been for a more impactful storm for the Mid-Atlantic through coastal New England due to a westward shift in the track. Below is the latest ensemble guidance from the European model. Each different ‘L’ you see on the map indicates where the center of the low pressure with this next storm may be positioned. Some of these ensemble members take this storm close enough to the coast for impacts.
Tuesday evening into the first half of Tuesday night, a light snow is possible in the eastern Ohio River Valley, the Nashville area, the peaks of the southern Appalachians, much of West Virginia, southwestern Pennsylvania, and western Virginia. Then overnight Tuesday, the snow will expand as colder air works in from the north as cold air wedges in. Snow is possible across the eastern Ohio Valley, the southern and central Appalachians, western North Carolina, much of Virginia, Maryland, Delaware, and southern New Jersey. The snow will even expand as far north as New York City and Long Island depending on the track. Then on Wednesday, rain will begin to mix in with much of the snow due to warming temperatures. This is expected across the Ohio Valley and Appalachians while the snow persists in Virginia, north-central North Carolina, Maryland, the DelMarVa before winding down and turning into a mix or just rain by Wednesday afternoon. Meanwhile in the New York City area and into southern New England, snow is possible. Then by Wednesday evening, much of the activity in the Mid-Atlantic region will move offshore. Depending on the advance of the cold air, rain may changeover to snow along coastal Virginia and the northern Outer Banks — and yes, it’s mid-March. This is very unusual. In southern New England, the snow will persist into Wednesday night. Some of that snow may expand into eastern New England as well, but it’s too early to know.
This forecast remains highly uncertain. It’s important that you monitor the forecast from WeatherOptics as the forecast confidence becomes greater.