THE TAKEAWAY:
- A possible nor’easter may develop later this week, bringing snow, rain and strong winds.
- One forecast scenario sends the storm inland through the Ohio Valley and eastern Great Lakes.
- Other model projections show the system developing closer to the East Coast.
- Colder air is expected to surge into the eastern United States later this week.
A major weather pattern shift is expected to unfold late this week as a potential nor’easter takes shape near the Northeast and New England, followed by a sharp blast of cold air across much of the country.
The transition will begin as colder air pushes into the eastern United States while warmer conditions expand across the West.
That temperature contrast could help fuel a storm system capable of producing rain, snow and powerful wind gusts along and near the coast from Thursday into Saturday. The storm’s departure would then open the door to a significant cooldown across the East.
A strengthening ridge over the western United States is helping drive Canadian air southward into the Northeast as warmth builds farther west. That configuration supplies the lift and upper-level energy needed for low pressure to intensify, setting the stage for the late-week storm.
Rather than reflecting a typical El Niño setup, the pattern is being shaped by the polar jet stream. A southward dip in that jet could allow the storm to first form somewhere between the Great Lakes and Ohio Valley before strengthening.
An unusually early disruption of the stratospheric polar vortex high above the Arctic has also contributed to the broader weather pattern.
Nor’easter Potential
Because the pattern remains highly dynamic, forecast models have yet to settle on the precise track and potential impacts of the possible nor’easter.
In one projection, a primary low-pressure system moves inland through the Ohio Valley and eastern Great Lakes before gradually transferring its energy to the coast, where a secondary low could form.
With that setup, the immediate coastline and I-95 corridor would likely stay relatively dry. Farther inland, especially across higher elevations, increased moisture could produce accumulating snow.
Another model scenario places the nor’easter much closer to the Eastern Seaboard. A coastal system developing in that position would bring more substantial impacts, including periods of heavy rain and strong winds.
Snow would remain possible inland, although limited cold air would likely keep the heaviest accumulations confined to elevated terrain.
A key wildcard in this scenario is whether the storm instead tracks farther offshore into the open Atlantic.
A storm path too far east would push much of the precipitation away from the coast, sharply reducing the threat of coastal rain and wind while also limiting inland snowfall.
Forecasters do not currently favor that outcome, but it remains possible with several days still to go before the system develops.
What We Know
What appears increasingly likely is that a low-pressure wave will organize over the Ohio Valley late Wednesday before moving toward the Mid-Atlantic and Northeast by Thursday evening.
The system is expected to spread rain across much of the East, while accumulating snow will be most likely in the higher elevations of New England and the interior Northeast.
Although the supply of cold air will be limited, snow is still possible in parts of Maine, Vermont, New Hampshire and upstate New York, with flakes potentially reaching south into the Appalachians.
Regardless of the storm’s final path, any snow mixing in near the coast or along the I-95 corridor is unlikely to accumulate.
Periods of rain, relatively warm ground temperatures and insufficient cold air will make it difficult for snow to stick.
Day-by-Day Timeline
According to the FOX Forecast Center, the system will begin organizing as it crosses the Great Lakes and Ohio Valley. Initially, the low will be weak and poorly defined, producing scattered light rain with limited impacts.
By Thursday, the initial low will move toward the Northeast. With colder air remaining to the north, precipitation will fall mainly as rain.
Scattered showers may reach the I-95 corridor and create minor travel delays, but widespread disruptions are not expected at that point.
On Friday, the low will approach the coast and try to strengthen. Since cold air will still be limited, the greatest potential for accumulating snow will remain across northern New York, Vermont, New Hampshire and Maine.
That is when the two primary forecast scenarios become especially important.
If a secondary coastal low does not form near the Mid-Atlantic, impacts along the I-95 corridor would probably stay limited, while snowfall amounts farther inland could be lower.
But if a secondary low develops farther south and offshore, coastal communities could see stronger wind gusts and perhaps a brief changeover from rain to snow as the storm exits.
By Saturday, the system should pull away toward Canada. Even so, lingering moisture combined with colder northwest winds could generate snow showers from Maine southward through the Appalachians, including parts of upstate New York and central Pennsylvania.
Behind the departing storm, a late-fall air mass will spread across the region, driving afternoon temperatures into the 30s for more than 110 million people in the Northeast and nearby areas.
A split in temperatures trailing behind
Canadian cold air will begin spreading across the eastern United States late Friday.
Afternoon highs may struggle to reach the 30s and 40s across the Northeast, Great Lakes and Ohio Valley, while overnight lows fall into the 20s.
That cold air could potentially reach the Gulf Coast and Florida by Sunday.
“To give an idea of how big the swing could be, on Tuesday over 300 million Americans will be above average and only a little over 4 million Americans will be below average,” according to the FOX Forecast Center reports. “By Saturday, that number exceeds 160 million Americans below average and likely even higher into Sunday.”
As the eastern United States turns colder, the West is expected to remain warmer and drier.
Temperatures from California across the Great Basin and into the desert Southwest could run 10 to 20 degrees above average.
