Nor'easter walloping parts of Northeast with cold rain, April snow

A nor'easter was lashing the Northeast on Friday, bringing major weather changes to the region. AccuWeather meteorologists, who have been keeping tabs on the storm all week, warn that it will strengthen quickly enough to unleash a soaking rain and colder air in New England and the upper part of the mid-Atlantic and a heavy snowfall in the higher elevations in true nor'easter fashion into Friday.

A nor'easter is simply any large storm that brings northeasterly winds along the Atlantic coast of North America, according to the National Weather Service (NWS) definition.

Even though explosive strengthening is not expected, the storm will develop enough to cause winds to increase along the upper mid-Atlantic and New England coasts to create nor'easter conditions. Winds from the northeast are forecast to pick up and average 15-25 mph with gusts up to 40 mph from northern New Jersey to Maine at the storm's peak during Friday and Friday night. Few problems are expected from the storm's winds other than creating a period of rough seas along the coast and over offshore waters of New England.

In this satellite image, clouds can be seen gathering along the mid-Atlantic and New England coasts in response to a developing nor'easter on Thursday, April 15, 2021. (CIRA at Colorado State/GOES-East)

The main impacts from the storm will be due to its precipitation.

As the storm organizes, it will tap into colder air aloft and allow rain to change to snow from high to intermediate elevations in eastern New York state and much of New England, according to AccuWeather Senior Meteorologist Brett Anderson.

"An inch of snow can accumulate at elevations as low as 750 feet, while snowfall will ramp up at progressively higher elevations," Anderson said.

Several inches of wet snow is forecast with upwards of 6 inches over the ridges in the Berkshires, Adirondacks and the Green and White Mountains. The highest elevations of the Green and White Mountains can pick up 10-20 inches of snow. Farther south, up to a few inches of snow can pile up over the higher elevations of the Catskills.

"There is even the chance that snow briefly mixes in along the coast of Massachusetts, including in the Boston area, as well as in coastal areas of New Hampshire and Maine on Friday," Anderson said.

A bit of snow is also expected to fall either mixed with rain or briefly in pure form on the mountains of western Pennsylvania, western Maryland, western New York state and northeastern West Virginia for a time on Friday.

Most of the roads at lower elevations in the Northeast will be just wet. Secondary roads that venture over the high ground can become slushy and snow-covered, even though it is the middle of April and the bulk of the snow is expected to fall during the daylight hours on Friday.

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Many in the Northeast may not be looking forward to a cold rain or snow, especially after warm weather so far this month. For instance, the average temperature in New York City has been 3.2 degrees Fahrenheit above normal thus far in April. Philadelphia's average temperature has been 2.8 degrees above normal.

Farther north, where the weather is expected to be even more wintry late this week, the warm trend has even more notable. Boston has been 4 degrees above normal through mid-April. Interior areas like Pittsburgh have had even more extreme departures from normal. The Steel City's average temperature through April 14 was 5.7 degrees above normal.

However, many of these places have also experienced a drier-than-average spring, so moisture from the storm is greatly needed across parts of the region. Soil conditions range from average to that of moderate drought across New England and New York state, according to the United States Drought Monitor.

"The low-elevation rain and mountain snow will help to alleviate the dry conditions in the region at a critical time with the approach of the warm weather and growing season," Anderson said.

The storm is forecast to bring 1-2 inches of rain to most locations -- or the equivalent of 1-2 inches of liquid from melted snow. However, local amounts of up to 4 inches are predicted from central New England westward to eastern New York state.

Even though the moisture is needed, too much rain may fall too fast and lead to quick runoff at low elevations. The bulk of the moisture is expected to occur in 36 hours or less into Friday evening. The runoff may lead to urban flooding as well as rapid rises on small streams.

Philadelphia and Washington, D.C., are likely to miss the bulk of the storm's rainfall with only spotty showers anticipated, but the swath from New York City to Boston is expected to receive a thorough soaking that could lead to slow travel and ponding on some low-lying roadways. The worst conditions in New York City are likely into Thursday night, while Boston will bear the brunt of the rain from later Thursday night into Friday.

Snow during April is not unusual especially over the higher elevations of New York state and New England. In fact, just last year, several inches of snow fell on part of the region on April 18. During that storm, Worcester, Massachusetts, picked up 4.7 inches of snow. The same storm brought nearly an inch of snow to Boston and 2.4 inches of snow to Windsor Locks, Connecticut.

Many cities in the Northeast get at least a little snow in an average April, AccuWeather Meteorologist Jake Sojda said.

"Albany, New York, averages 2.1 inches of snow in April," Sojda explained, adding, "The last time Albany didn't record any snow in April was in 2012."

On April 9, 2000, a spring snowstorm dumped 13.3 inches of snow on Albany.

AccuWeather meteorologists are not expecting that kind of snow accumulation on low elevations around Albany with this storm, but a small slushy accumulation of snow can occur in the New York state capital. Grassy areas of the lower Hudson and Connecticut valleys can be whitened by some snow.

No snow of consequence is forecast for New York City, but there can be some wet snow mixed in at times in Hartford, Connecticut, on Friday.

Parts of the Northeast have received accumulating snow well into May and not even just confined to high elevations. Albany managed to pick up 2.2 inches of snow on May 18, 2002.

It has snowed all the way to sea level in May in New England. Boston's latest snowfall on record was 0.5 of an inch that fell on May 10, 1977. That same storm brought more than a foot of snow to the highest elevations of western Massachusetts with close to 7 inches reported in Providence, Rhode Island.

The coldest air will be locked up in close proximity to the storm, but milder air will begin to filter eastward over the weekend. In general, the weather will be improving over the weekend, AccuWeather forecasters say. However, very spotty showers can't be ruled out.

In places where the sky manages to clear out and winds drop off at night over the weekend, there can be a bit of frost in the normally cold spots of the central Appalachians and interior New England. In many cases, though, cloud cover may prevent frost from forming this time around.

That may not be the case later in the month as a major push of cold air is forecast to invade the Central states later this weekend to next week.

Even though the main thrusts of cold air may hold up west of the Appalachians, some cold nights are likely in store for the Northeast. Temperatures could drop low enough to be of concern. Frosts or freezes may develop where budding and blossoming fruit trees, berry bushes and vineyards are underway during late April to mid-May, AccuWeather Lead Long-Range Meteorologist Paul Pastelok said, adding that these plants are most susceptible to damage when budding is occurring.

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