A triple threat of heavy inland snow, coastal flooding and strong winds appears increasingly likely for much of southern New England, New York and perhaps parts of the Mid-Atlantic on Monday into Tuesday, with lingering impacts possible into Wednesday. As of now, the best chance of significant snow or ice looks to be north and west of major urban areas along the Interstate-95 corridor, including Philadelphia, New York City and Boston, but there is still time for the storm track to shift.
For locations that do see significant snowfall from this storm, it could easily turn into the biggest event of the cold season, given that most of the Northeast is running way behind average for snowfall this winter.
While weather models are in general agreement that an intensifying area of low pressure will track from near the Carolina coast to around southeast Massachusetts on Monday and Tuesday, confidence in specific impacts remains low for a number of reasons.
Several key factors are cause for caution when it comes to forecast confidence:
- Temperatures are forecast to be only marginally cold. Even in interior regions away from the coast, temperatures during the storm may not drop too far below freezing. The storm could pull in some colder air from northern New England and near the Great Lakes, but it is in relatively limited supply.
- How quickly the storm does or does not develop can result in a significant change in track and where the rain-snow line sets up.
- The storm is forecast to rapidly intensify thanks to the anticipated merger of jet streams. Details on this process are often tough to pin down until closer to the event. If the merger is slow to evolve, the storm could be weaker than expected and further out to sea.
A more wintry weather pattern
Despite the uncertainties, the stage is certainly set for what could end up a blockbuster March storm. Not only has weather modeling come into greater agreement that a major storm will develop, but also the large-scale weather pattern is more supportive of such a storm than it has been most of this winter.
While a powerful jet stream over the Pacific Ocean continues to fire hose the West with flooding rain and mountain snow, a brief area of high pressure is set to flex across the Mountain West early next week. An area of high pressure in that location, which has been lacking this winter, can be conducive to formation of nor’easters.
This potential storm also comes during a period of high-latitude “blocking,” which is when an area of high pressure becomes stagnant near Greenland, that tends to favor storms tracking near the East Coast while feeding colder air southward.
Plus, there’s also precedent for an active storm pattern in the eastern United States after disruption of the polar vortex, a process that has been underway throughout the month. As recently as March 2018, a string of nor’easters developed in the wake of a jostling of the polar vortex.
The National Weather Service’s Weather Prediction Center (WPC) is among those forecasting a major storm, with a low pressure of 1008 millibars near the Outer Banks of North Carolina by around sunrise Monday dropping to 992 millibars off the coast of southern New England 24 hours later. That’s a 16 millibar drop.
There’s even a chance this storm could end up a “bomb cyclone,” which occurs when the central pressure of a storm system drops at least 24 millibars in 24 hours. It’s a feature of many historic storms and also seems to be occurring more often in a warming world.
In the currently favored scenario, precipitation focuses on the Mid-Atlantic on Monday as the developing low pressure climbs the coast. By Monday evening, rain and heavy snow would work into southern New England and adjacent areas. Rain, snow and strong winds would then continue through Tuesday across much of New England.
Aside from what could be inches of rain near the coast and the potential for feet of snow inland, high winds and prolonged onshore flow are also likely.
If the storm does rapidly intensify, damaging gusts to 60 or even 70 mph are possible near the shore and maybe inland. Coastal flooding and battering waves would also occur. Fortunately, the storm is not coinciding with the time of the month when the moon can make tides higher than usual.
There is some chance the storm could stall in the area through midweek, with precipitation rates likely dropping after Tuesday but gusty winds lingering.