Weather Outside Your Window: Tropical rainstorm could spoil warmup in mid-Atlantic, New England

A warmup is on the way for the weekend, but rainy and windy conditions on the coast could keep some residents chilly.

By Alex Sosnowski, AccuWeather senior meteorologist

Published Oct. 19, 2022 12:10 PM CDT | Updated Oct. 20, 2022 12:40 PM CDT

Clouds, rain and breezy conditions will develop as a tropical rainstorm takes shape just offshore of the East coast of the United States this weekend. But, how cool and nasty the weather becomes in the mid-Atlantic and New England will depend on the track, strength and nature of the storm into early next week, AccuWeather meteorologists say.

Temperatures will rebound by 10-20 degrees Fahrenheit or more across much of the eastern part of the U.S. in the coming days in the wake of an outbreak of cold air more fitting for December. For areas near and west of the Appalachians, the warmup will get rolling on Thursday and Friday and continue right through the weekend and into early next week.

However, the development of a storm just offshore of the southeastern U.S. has been on AccuWeather meteorologists' radar since Hurricane Ian departed. That storm will play a role in the amount of cloud cover and extent of rain as well as how strong winds become and how rough surf conditions get from eastern North Carolina to New England.

“If the storm hugs the coast, it would push rain into the Philadelphia and New York City on Sunday and into Boston by Sunday night," said AccuWeather Senior Meteorologist Dean DeVore.

Even a relatively weak storm that stays 50-100 miles offshore could still throw clouds and some rain back toward the mid-Atlantic and New England coasts, with breezy conditions and choppy surf from the North Carolina Outer Banks to Long Island, New York, and Cape Cod, Massachusetts.

"But, if the storm develops to its full potential, it could generate heavy rain and urban flooding across the Interstate 95 corridor of the Northeast, along with strong winds that lead to coastal flooding from Sunday to Monday,” DeVore said.

A stronger storm would also trigger soaking rain farther inland, perhaps as far west as the central Appalachians and northern New England.

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The amount and duration of rain will play a role in how much temperatures will be suppressed. Where rain falls most of the time, temperatures may be knocked down by 10-20 degrees or more from their forecast above-average levels in the 60s and lower 70s on Friday and Saturday. Temperatures could hover in the 50s and even the 40s during the rain on Sunday and Monday.

AccuWeather meteorologists are also monitoring the potential for the coastal storm to develop some tropical characteristics, especially since the system will have access to moisture as far south as the Caribbean. The area off the southeastern U.S. coast is part of a zone that extends from the Caribbean to the western and central Atlantic where there tends to be tropical development during late October and November.

Because of the potential for copious amounts of tropical moisture to be drawn into a weak low pressure area, AccuWeather meteorologists will be referring to the feature as a tropical rainstorm and one that could unleash flooding rainfall in a portion of the Northeast from later this weekend to early next week.

Since the storm will form over water temperatures in the 70s and 80s F in the Gulf Stream along the East coast of the U.S., there may be enough time for the system to develop a warm core at least in part, AccuWeather Senior Meteorologist John Gresiak explained. Having a warm core is one key requirement for a storm to be considered tropical.

In this case, a tropical depression or tropical storm could evolve, as a long shot, with a well-defined circulation and low-pressure center. A tropical depression typically has sustained winds around 35 mph, while a tropical storm packs sustained winds of 39 mph to 73 mph. Lisa is the next name on the list of tropical storms for the 2022 Atlantic hurricane season.

"There is a somewhat greater chance for the system to become a hybrid or subtropical system that has some tropical and some non-tropical aspects," Gresiak said. With a subtropical system, a more broad circulation tends to form with a poorly-defined center and pockets of dry air and gusty winds.

There is a chance the storm remains devoid of tropical characteristics and simply becomes a nor'easter.

Following a lack of rain much of the summer, storms have been providing some soaking downpours during the official start of the autumn season and have begun to erase the dry and drought conditions in the Northeast.

The region could still benefit from another soaking -- but non-flooding -- rain event as long-term soil and watershed conditions range from abnormally dry to extreme drought in parts of the upper mid-Atlantic to southern New England, based on the United States Drought Monitor reports from mid-October.

For those looking to attend outdoor sporting events, chilly rain is not desirable. There is a chance that rain could come calling on Sunday for both Major League Baseball championship games in Philadelphia and New York City. Rain is possible for the NFL games on Sunday in Baltimore and Summerfield, Maryland, and on Monday night at Foxboro, Massachusetts.

In the wake of the storm's influence, the warmth that builds over the Central states into this weekend is likely to surge eastward for a few days next week.