A potential nor’easter could bring impacts to the Northeast late this week into the weekend. 

Cold air coming right before means that there is a chance for snow as well as heavy rain, gusty winds and the first frost and freezes for millions.

What we know

There is still uncertainty about how this potential nor’easter will form as models will come into agreement later this week. But let’s start with what we are most certain about.

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It will get cold: A deep dip in the jet stream, called a trough, is expected across the East late this week. So get outside and enjoy the above average temperatures while you still can. 

The highs will plummet 20 degrees from Wednesday to Friday from Chicago all the way to Atlanta. By the weekend, lows will drop to the 30s as far south as the Florida Panhandle. 

A low will develop: The latest models show a low pressure system moving across the Midwest by Wednesday. It will begin to strengthen as it moves into the Ohio Valley Wednesday night, bringing rainfall from Georgia to Michigan. 

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This low will shift east and will roughly reach the Appalachian Mountains and will begin to interact with the cold air that will be surging south. 

By Thursday night, we should start to see the first chances of snow across interior regions of the Northeast.

Some of this snow will be from lake-effect snow bands, caused by this cold air moving off the relatively warm waters of the Great Lakes. These lakes bring the moisture that clashes with that cool air, which forms the narrow and potentially heavy bands of lake-effect snow. 

(MORE: Lake-effect snow and El Niño)

Friday into the weekend

This is where it gets a little bit more uncertain. The European and the American models have a pretty sizable disagreement for what this low will do.

While both systems call for the low to track across the Midwest (the American, also called the GFS, has it a little farther north), what happens next is what gets interesting. The GFS has the low essentially slow to a crawl, bringing rounds of lake-effect snow across the interior Northeast and rain to the I-95 corridor through the weekend and potentially into early next week. 

The Euro has the storm move at a more traditional speed. This model calls for the storm to move offshore and bring rain, winds and snow inland Friday and Saturday before moving on. 

With low temperatures expected to remain above freezing for the I-95 corridor at this time, we do not expect snow for the major metropolitan areas. But, the rain/snow line isn’t too far away, so if you want to see snow, you will not have to travel far. 

What is a nor’easter?

Depending on where you live, this term can make you shudder. But, the criteria to meet to qualify as a nor’easter is simpler than you may realize. 

A nor’easter is just when an area of low pressure off the East Coast brings winds in from the northeast. That is it. 

So, nor’easters can happen all year round and don't necessarily bring heavy snow. They are more frequent in the winter months, and should we have cold enough air, that is when the snow falls. 

We will continue to monitor this situation as the week progresses, so check back with us to monitor any changes in the forecast. 

(MORE: What is a nor'easter?)

Rob Shackelford is a meteorologist and climate scientist at weather.com. He received his undergraduate and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.