Potential nor’easter could bring rain and snow later this week

A possible nor’easter could impact the Northeast and Great Lakes late this week and into the weekend.

Cold air arriving just ahead means there is a risk of snow as well as torrential rain, gusty winds and the first frost and freeze for millions of people.

What we know

There is still uncertainty as to how this potential nor’easter will form, as the models agree later this week. But let’s start with what we are most sure of.

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It’s going to be cold: A deep southward dive in the jet stream, called a trough, is expected to cross the East late this week. So get outside and enjoy the above-average temperatures while you still can.

Daytime high temperatures will drop 20 degrees Wednesday through Friday from Chicago to Atlanta. By the weekend, lows will drop into the 30s as far south as the Florida Panhandle.

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

By Thursday evening, we expect another area of ​​low pressure to form off the East Coast. At this time, rain may mix with wet snow or change to wet snow over parts of the interior Northeast.

Friday in the weekend

This is where forecasts become more confusing and uncertain, which is not unusual for coastal storm forecasts several days out.

Some forecast models surround the low near the coast for some time, which would bring a threat of strong wind gusts and coastal flooding during high tide to parts of the East Coast, from the Outer Banks of northern North Carolina to New England.

It could also lead to heavier precipitation – both rain near the coast and snow inland in the northeast.

Other model forecasts are a little further east off the East Coast, with generally lighter rain and snow inland, less strong winds on the coast, but still some threat of coastal flooding at high tide.

The map below shows our latest forecast for snow and rain from this system through Sunday.

The best chances for accumulating snow extend from the northern New England mountains to upstate New York and the Appalachian Mountains.

With low temperatures expected to remain above freezing across the I-95 corridor, we do not expect snow for major metro areas.

Some wet snow could fall in lake-effect bands, caused by this cold air moving away from the relatively warm waters of the Great Lakes. These lakes provide moisture that conflicts with this cool air, which forms the narrow bands of lake-effect rain and snow.

This snow would be the “first of the season” in many of these regions.

This forecast is likely to change a bit over the next few days as model forecasts begin to move closer to scenario. Check back with us at Weather.com for updates.

(MORE: Lake Effect Snow and El Niño | When does the first snow usually fall?)

What is a nor’easter?

Depending on where you live, this term may make you shudder, but the criteria for being called a nor’easter is simpler than you think.

A nor’easter occurs just as an area of ​​low pressure off the East Coast brings northeasterly winds – that’s it.

Thus, nor’easters can occur all year round and do not necessarily bring heavy snowfall. They are more common during the winter months, and if the air is cold enough, snow falls more widely.

(MORE: What is a nor’easter?)

Rob Shackelford is a meteorologist and climatologist at Weather.com. He earned his undergraduate and master’s degrees at the University of Georgia, where he studied meteorology and experimented with alternative hurricane forecasting tools.