A possible nor’easter later in the week will bring first frost and snowfall to the east. A possible nor’easter could cause impacts across the Northeast and Great Lakes later this week into the weekend. The cold air arriving just ahead of time means there is a chance of snow, as well as torrential rain, gusty winds and the first frost and frost for millions. What We Know There is still uncertainty about how this potential nor’easter will form, as models will come to an agreement later this week. But let’s start with what we are most sure of. It will be cold: A deep dip in the southward jet stream, called a trough, is expected to move across the east later this week. So get out and enjoy the above-average temperatures while you can. Daytime highs will plummet 20 degrees Wednesday through Friday from Chicago to Atlanta. By the weekend, lows will drop into the 30s into the southern Florida Panhandle. A Low Will Develop: The latest models show a low pressure system moving across the Midwest on Wednesday. It will begin to strengthen as it moves into the Ohio Valley Wednesday night, bringing rain from Georgia to Michigan. Get more of our news on Google Set The Weather Company as a ‘preferred source’ for faster access to the news you value. By Thursday night, we expect another area of low pressure to form off the east coast. By then, rain could be mixing with wet snow or changing to wet snow in parts of the interior Northeast. Friday through the weekendThis is where the forecast becomes more confusing and uncertain, something that is not unusual for coastal storm forecasts several days away. Some model forecasts keep the low near the coast for a while, which would bring a threat of strong wind gusts and coastal flooding during high tide to parts of the East Coast from North Carolina’s Outer Banks north to New England. That could also include heavier precipitation, both rain near the coast and snow inland in the Northeast. Other model forecasts are a little further east of the East Coast, with generally lighter inland rain and snow, less strong winds on the coast, but still some threat of coastal flooding at high tide. The map below shows our latest snow and rain outlook for this system through Sunday. The best snow accumulation chances extend from the mountains of northern New England to upstate New York and the Appalachians. With low temperatures expected to remain above freezing along the I-95 corridor, we do not expect snow in major metropolitan areas. Some wet snow could fall in lake-effect bands, caused by this cold air coming off the relatively warm waters of the Great Lakes. These lakes supply moisture that collides with cold 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 areas. This forecast will likely change somewhat over the next day as model forecasts begin to move closer to the scenario. Check back with us at Weather.com for updates. (MORE: Lake Effect Snow and El Niño | When the First Snow Usually Falls) What is a nor’easter? Depending on where you live, this term may make you cringe, but the criteria for qualifying as a nor’easter is simpler than you might imagine. A nor’easter is just when an area of low pressure off the east coast brings in northeasterly winds, that’s all. They are more frequent in the winter months and, if we have cold enough air, that is when the most snow falls. (MORE: What is a Northeastern Easter?) Rob Shackelford is a meteorologist and climate scientist at Weather.com. He received his bachelor’s and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.
