A significant change to the nation’s weather is taking shape late this week, with a potential nor’easter impacting the Northeast and New England before ushering in a cold blast to the country. 

The change will start when colder air shifts into the eastern United States with warmer weather building across the West.

The shift in temperatures is setting the stage for a developing system that could bring rain, snow and gusty winds off the coast from Thursday through Saturday. This will pave the way for a big temperature drop across the East.

A strong ridge is building over the western United States and is helping colder Canadian air to punch south into the Northeast, while warmer air builds in the West. This provides a lift and upper-level energy needed to support a strengthening area of low pressure, setting the state for the late-week storm. 

Instead of this being the typical El Niño pattern, this is the polar jet stream making an appearance. The dip in the polar jet stream will allow for the storm to initially originate somewhere from the Great Lakes to the Ohio Valley, setting the stage for the strengthening system. 

As well, the unusually early disruption of the stratospheric polar vortex high above the Arctic has also helped support this larger weather pattern. 

Nor’easter potential

With such dynamic weather patter unfolding, forecast models are still showing some uncertainty surrounding the track and impacts of a potential nor’easter.  

In one scenario, an initial area of low pressure tracks inland across the Ohio Valley and eastern Great Lakes before gradually transferring its energy offshore, allowing a secondary coastal low to develop.

Under this setup, the immediate coast and I-95 corridor would remain on the drier side. Meanwhile, inland and higher-elevation areas could pick up moisture, bringing accumulating snow.

In another scenario, forecast models suggest the nor’easter to track much closer to the Eastern Seaboard. The storm would develop closer to the coast, bringing more significant impacts to those areas, including periods of heavy rain and gusty winds.

Inland areas could still see snow, but accumulations would likely be limited by a lack of cold air, keeping the heaviest totals confined to higher elevations.

One wildcard in this second scenario is the possibility that the storm tracks farther offshore into the open Atlantic.

A track too far east could push the precipitation away from the coast, significantly reducing the potential for coastal rain and wind while also limiting snow inland. 

While this scenario is not favored at this time, it cannot be ruled out given the number of days remaining before the storm develops.

What we know

What is becoming clearer is that a wave of low pressure will organize across the Ohio Valley late Wednesday before tracking toward the Mid-Atlantic and Northeast by late Thursday.

The developing system is expected to spread widespread rain across the East, with accumulating snow most likely across the higher elevations of New England and the interior Northeast.

Although cold air will be limited, some snow is still expected across parts of Maine, Vermont, New Hampshire and upstate New York, with snow potentially extending south into the Appalachians.

Regardless of the storm’s eventual track, any snow that mixes in closer to the coast along the I-95 corridor is unlikely to accumulate. 

Intermittent rain, surface temperatures and a lack of cold air will make it difficult for the snow to stick.

Day-by-day timeline

According to the FOX Forecast Center, the system will begin taking shape as it moves across the Great Lakes and Ohio Valley. At this stage, the low-pressure system will remain relatively weak and disorganized, producing scattered light rain with minimal impacts.

By Thursday, the initial low will advance toward the Northeast. Cold air will remain to the north, causing mostly rain. 

Scattered showers could reach the I-95 corridor and cause minor travel delays, but overall impacts are expected to remain limited.

On Friday, the low will track toward the coast and attempt to strengthen. With cold air still limited, the best chances for accumulating snow will be concentrated across northern New York, Vermont, New Hampshire and Maine.

This is where the two forecast scenarios outlined above become important.

If a secondary coastal low fails to develop near the Mid-Atlantic, impacts along the I-95 corridor would likely remain minimal, while snowfall totals farther inland could be lighter.

However, if a secondary low develops farther south and offshore, the coastal corridor could experience stronger wind gusts and potentially a brief transition from rain to snow on the back side of the departing system.

By Saturday, the storm is expected to pull away toward Canada. However, moisture and colder northwesterly winds could bring lingering snow showers from Maine south through the Appalachians, including parts of upstate New York and central Pennsylvania.

Behind the departing storm, a late-autumn air mass will settle across the region, sending afternoon temperatures into the 30s for more than 110 million people across the Northeast and surrounding areas.

A split in temperatures trailing behind

Beginning late Friday, cold air from Canada will spread across the eastern United States.

High temperatures could remain in the 30s or 40s across the Northeast, Great Lakes and Ohio Valley, with lows plummeting into the 20s.

Along with that, there is a possibility that this cold air could 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.”

While the eastern United States is under a cold spell, the west will experience warmer and drier conditions.

Cities from California to the Great Basin and desert Southwest could see temperatures 10-20 degrees above average.