A slow-moving storm system will be heading up the eastern seaboard of the US at the end of this week, becoming the culprit for days of rain and snow across the northeastern US. The storm is originating from the Gulf of Mexico, where it has already dropped widespread rainy and gloomy weather earlier this week across parts of the south and southeast.
Now that Spring is upon us, snow chances are gradually decreasing, but as we remain in the month of march, sneaky winter storm opportunities are always still a threat. The storm system that will move north tonight and tomorrow will bring heavy snowfall to interior portions of the Northeast, along with heavy rain and gusty winds across the coastal plain. As the storm pulls away there will even be the risk for some snow closer to the coast as strong dynamics lead to cooling under the heaviest precipitation.
Low pressure will rapidly strengthen off the Mid-Atlantic coast Thursday night with a minimum central pressure of about 1000 mb. By Friday night however, only 24 hours later, the pressure is expected to be down to around 980 mb. It’s even conceivable the storm briefly dips into the upper 970 mb range. Should this be the case, we’d be looking at a rather classic storm undergoing bombogenesis.
Impacts will begin tonight as a slug of light to moderate rain begins to enter the Mid-Atlantic east of the Appalachian Mountains. By Thursday, all of the Mid-Atlantic will be dealing with this rain, possibly even extreme western portions of New England. Some of this rain will be heavy since the storm will be aided by the Atlantic Ocean’s moisture. Moisture may even tap into the Caribbean Sea for a time. It’s once we get into Thursday evening that pockets of snow are expected to develop across parts of Upstate New York and the Catskills.
This area of snow will rapidly overspread the interior Northeast as Thursday night progresses thanks to air rapidly cooling under heavier precipitation. Some of this will be due to the radiational cooling since the sun will be down but some of this will also be due to evaporational cooling. This process takes place when an intensifying storm — like this one — causes upward motion and heavy precipitation, which therefore causes the air below to cool. That’s why snow will become widespread from northeastern Pennsylvania through northern Vermont and New Hampshire overnight Thursday.
By Friday, the center of the low pressure system will clip Cape Cod as it moves in a north-northeast direction. Moderate to heavy rain will be lashing southern and eastern New England while snow continues to fall over the mountainous areas of northern New England and the western Mid-Atlantic, including western Pennsylvania, New York and Upstate New York. Another issue that will be present are the winds. Since this storm system will be intensifying into a strong low pressure, there will likely be intense winds. Widespread wind gusts of 20-45+ mph are forecasted across the Northeast between Friday and Saturday, which may lead to scattered power outages for a time.
Friday night, the rain will end for most of the coastal areas of New England while the snow persists inland. What will be interesting to watch is the intrusion of cold air from the north and west, dropping temperatures to below freezing across most of New England and the northern Mid-Atlantic. Depending on how much moisture will still be in place on the backside of the storm will determine how much snow — if any — affects the lower elevations and coastal areas of New England. The morning run of the European model, for example, brings a period of moderate to heavy snow close to the coast early Saturday morning.
By Saturday mid-morning and afternoon, however, the main impacts from this storm will be over as it continues to pull away to the north and east. Lingering snow showers will persist across the interior Northeast, especially in the morning, before all of the precipitation ends by Saturday night.
A widespread 6-15 inches of snow is expected to fall across the interior Northeast thanks to this late-season winter storm while a general 0.5 to 2 inches of rain falls in the Mid-Atlantic.