This image for Sunday, July 16, 2023, shows the amount of water in the atmosphere that could be unleashed by downpours and thunderstorms. This plume of moisture is forecast to pivot into much of New England Sunday night. ACCUWEATHER.
As more rounds of torrential downpours crawl through the northeastern United States, the likelihood of damaging and life-threatening flash flooding will increase into the middle of next week, AccuWeather meteorologists warn. Flooding may occur in some areas that were hit hard last Sunday and Monday and is also likely in many areas that missed out on the deluge in recent days.
Meteorologists at AccuWeather have raised concerns about a high-powered rainmaker, known as an atmospheric river, which may affect the Northeast from early Sunday to Sunday night. “The atmospheric river will drench the region with a “fire hose” of moisture,” said weather experts.
Atmospheric rivers have been responsible for tremendous flash flooding and river flooding in locations such as the Carolinas in years past, as well as in parts of California this past winter on multiple occasions.
Local rainfall amounts of 1–3 inches per hour can quickly overwhelm storm drains and small streams as each round of slow-moving thunderstorms rolls through. This risk will not only be of great concern in suburban and rural areas, but road closures due to flooding may also disrupt travel in some of the major metro areas in the Northeast, including New York City; Hartford, Connecticut; Providence, Rhode Island; and Boston.
But, even in cities farther to the south, in the mid-Atlantic, such as in Philadelphia, Baltimore, and Washington. D.C. where torrential downpours may be more spotty in nature, there is still the potential for dangerous and disruptive flash flooding as a result of 1–4 inches of rain. Much of that rain may fall in one or two brief episodes, which could cause rapid and excessive runoff.
“Motorists are urged to be prepared for street and highway flooding, even in some locations that do not typically take on water due to the extreme nature of the event,” said AccuWeather forecasters
One round of thunderstorms with excessive rainfall was moving slowly from just north of New York City to southern New England on Friday. If this complex of storms holds together or re-fires later on, the risk of flash flooding would expand into central New England and the middle part of the Hudson Valley during Friday evening. Flash flood dangers may reach portions of Vermont, New Hampshire, and Maine Friday night.
“Many parts of the region may get a break from thundery downpours on Saturday, which could be the best day of the weekend overall for travel and outdoor plans. There will likely be a few exceptions, however, and due to the amount of moisture in the air, any downpour will be capable of producing highly localized flash flooding,” said AccuWeather.
As a strong disturbance pivots in from the Midwest on Sunday, it will tap into tropical moisture over the Atlantic Ocean. An atmospheric river may unfold and unleash a plume of water where several inches of rain may fall over multiple hours, especially from parts of New Jersey, eastern Pennsylvania, and southeastern New York through New England.
Because of the larger, more intense scale of this disturbance, the likelihood of river flooding will increase in these areas. Some of the major rivers in the region that could be subject to moderate to major flooding are the Connecticut, Merrimack, Charles, and Passaic, to name a few. At the same time, flash flooding of small streams and low-lying areas is highly likely.
In a period of several hours to two days, an entire season’s worth of rain fell with widespread rainfall of 5–10 inches and locally higher amounts reported in parts of Vermont, eastern upstate New York, and western Massachusetts.
Experts strongly urge motorists never to drive through flooded roads. The road surface may have been washed away and swift-moving water may be much deeper than it appears. Campers should use extreme caution when setting up or hiking along small streams as a rush of water from downpours miles upstream could arrive without notice.
Additional rounds of rain are likely to occur into Wednesday and slowly push from the Midwest to the Appalachians, where flash flooding will also be likely, but spotty. Once again as these storms reach the coast, they will slow down, grab extra moisture and potentially unleash more widespread flooding.
However, more rain may be on the horizon for the Northeast next weekend.
Produced in association with AccuWeather
Edited by Judy J. Rotich and Newsdesk Manager
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