Weather Outside Your Window: 1st of 2 possible nor'easters poised to drench NYC to Boston

The first nor’easter of the season may become the third bomb cyclone in a matter of days to slam into the continental U.S., and it will usher in miserable conditions.

By Kevin Byrne, AccuWeather staff writer & Nicole LoBiondo, AccuWeather meteorologist

Updated Oct. 25, 2021 9:22 PM EDT

Flash flood watches were issued across parts of the mid-Atlantic on Monday afternoon as a powerful storm took shape off the Atlantic coast. The storm is poised to bring miserable weather conditions to areas from the mid-Atlantic coast to New England this week, and AccuWeather forecasters say it's just the first of multiple storms that take aim at the Northeast during the final week of October.

The storm has been categorized as a nor'easter since it will be spreading northeasterly winds along the coast and is the first such storm of the season to impact the region. The nor'easter is expected to quickly strengthen as it moves along the Eastern Seaboard but is expected to lose forward speed and become stationary off the Northeast coast late Monday evening.

As the storm strengthens, it could undergo a period of rapid intensification known as bombogenesis, which is when the central pressure of a storm drops by 0.71 of an inch of mercury (24 millibars) or more over a 24-hour period to become what is known as a bomb cyclone. Two similar storms developed in the northern Pacific and slammed into the western U.S. late last week and over the weekend.

Regardless of whether the nor'easter is classified as a bomb cyclone, it is likely to bring significant impacts to the Northeast.

With the rain forecast to begin late Monday evening and last into much of the day Tuesday, the National Weather Service issued a flash flood watch for New York City, starting at 8 p.m. Monday and lasting through 5 p.m. Tuesday. The New York City Emergency Management also issued a travel advisory for Monday evening through Tuesday afternoon.

"We know how quickly these storms can escalate, so everyone, especially those living in basement apartments, should plan accordingly," New York City Mayor Bill de Blasio warned over Twitter on Monday.

New Jersey Gov. Phil Murphy declared a state of emergency in preparation for the storm's impacts and urged residents to stay off the roads, stay vigilant and follow safety protocols. New York Gov. Kathy Hochul also declared a state of emergency for the Capital Region, Long Island, New York City, Mid-Hudson and Southern Tier regions.

“An early-season tempest could bring a wind-driven, chilly rain to portions of the Northeast from Monday through Wednesday," AccuWeather Meteorologist Randy Adkins said, adding that flooding could be a significant concern across southern New England.

Heavy rain will move into the New York City area Monday evening before it pushes into central and southern New England where it will continue to unload rain on Tuesday. The intense rainfall could result in flooding issues in low-lying and poor drainage areas. The rain is forecast to diminish in intensity by Wednesday morning, but some light rainfall could persist throughout the day near the coasts.

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AccuWeather forecasters say one added concern with the storm besides its strong winds and drenching rain is that it will target areas that were slammed by Tropical Storm Henri and Tropical Rainstorm Ida during the summer. Impacts from the storm in southern New England will be similar to what Henri caused in late August where travel delays and power outages were widespread.

The heaviest rainfall amounts are expected in Massachusetts, Connecticut and Rhode Island as a widespread 4-8 inches is predicted across these states.

Areas that experience particularly intense and long-lasting rainfall will pick up totals near the high end of this range, with an AccuWeather Local StormMax™ of 10 inches (250 mm) from Monday night through Wednesday.

Elsewhere, rainfall totals of 2-4 inches are forecast from far southern Maine through eastern New York and a large portion of New Jersey. Localized flooding cannot be ruled out, but flooding incidents will be less widespread. Travel delays could still become a problem where water ponds on roadways.

From Nova Scotia westward into the Adirondacks and south into eastern Pennsylvania and Delaware, 1-2 inches (25-50 mm) of rain are anticipated. Flooding will not be a substantial concern in this area. While some roadways may have standing water during periods of heaviest rainfall, impacts in this area will remain minor.

Defining features of a nor'easter can include howling winds that could be damaging at times. There will be no exception with this storm as winds are expected to gust from 40 to 60 mph from the coasts of New Jersey Tuesday to the southern shore of Nova Scotia in Atlantic Canada by Wednesday. The most intense winds will be confined to the Cape Code area and northward to coastal New Hampshire. Cities such as Provincetown, Plymouth and Boston, Massachusetts, could experience wind gusts from 60 to the AccuWeather Local StormMax™ of 80 mph Tuesday night.

As the storm intensifies off the New England coast Tuesday and Wednesday, blustery onshore winds reaching nearly 80 mph in spots will bring the possibility for coastal flooding, beach erosion and power outages. With a late start to the fall-foliage season underway across southern New England, many trees still have plenty of leaves on them, making the possibility for downed trees due to strong winds a possibility too.

Blustery conditions that will accompany this storm, along with the combination of clouds and rain, will produce AccuWeather RealFeel® Temperatures 5-10 degrees lower than the actual temperature Monday and Tuesday. This cooler change from the unseasonably warm conditions felt last week across much of the Northeast may be enough to result in some shock value for residents where temperatures averaged 5-10 degrees Fahrenheit above normal during the first 21 days of October.

Blustery conditions that will accompany this storm, along with the combination of clouds and rain will produce AccuWeather RealFeel® Temperatures 5-10 degrees lower than the actual temperature Monday and Tuesday. This cooler change from the unseasonably warm conditions felt last week across much of the Northeast may be enough to result in some shock value for residents where temperatures have averaged 5-10 degrees Fahrenheit above normal during the first 21 days of October.

AccuWeather Director of Forecasting Dan DePodwin said the storm could end up taking on tropical or subtropical characteristics by midweek. If that happens, the National Hurricane Center would give it the name Wanda, the final name in the Atlantic hurricane season's primary list of names.

"It would also be the first named stormed in nearly a month, which is unusual for October when there is typically a secondary peak of hurricane season," DePodwin added.

On top of that, AccuWeather meteorologists say the developing weather pattern will have staying power.

By Thursday, the nor'easter will move away from the eastern United States, and much of the Northeast will be able to dry out, while another storm is expected to approach the region from the west.

"The same massive storm that is currently bringing heavy rain, snow and strong winds to the Western states is expected to slowly move eastward across the country this week," AccuWeather Senior Meteorologist Brett Anderson explained.

The second storm also has the potential to become a nor'easter late this week and this weekend. It is unusual for multiple nor'easters to take aim at the region during this time of the year, according to AccuWeather Director of Forecasting Dan DePodwin.

That storm may bring another round of significant rain and strong coastal winds to the Northeast just in time for the Halloween weekend, potentially throwing a wrench in the plans of trick-or-treaters over the holiday weekend.