Downpours to douse US East Coast in wake of Beryl

As Beryl drenches the northern tier of the Northeast into Thursday, budding downpours along the Atlantic coast, that can lead to flash flooding, may be joined by new tropical area of interest into this weekend.

The main thrust of Tropical Rainstorm Beryl's downpours beyond Wednesday will focus on the St. Lawrence Valley and Maine before dissolving over southeastern Canada. However, AccuWeather meteorologists say downpours will erupt in the wake of Beryl's path along part of the Atlantic Seaboard into this weekend due in part to a new area of tropical interest.

Beryl will continue to move steadily along into the end of the week but will meet its demise over cooler air in eastern Canada. The system will continue the risk of severe thunderstorms and tornadoes into Thursday.

Before its exit, the tropical rainstorm will continue to unload locally heavy rain that can trigger flash flooding from northern New York to northern New England into Thursday night. A general 1-4 inches of rain will fall in this zone with local amounts of 4-8 inches from the Adirondacks to the mountains in northwestern Maine.

Beryl triggered rapid rises on secondary rivers in the region Thursday night with moderate to major flooding reported in some communities, including Lyndonville and Barre, Vermont. Parts of the region were flooded exactly one year ago. Beryl also sparked several reports of tornadoes in western and central New York.

"In some locations of the northern tier, rainfall rates of 1-2 inches per hour will occur and much of the total rainfall from Beryl may fall in six to eight hours," AccuWeather Meteorologist Alyssa Glenny said, "Hence the concern for flash flooding."

Downpours have a tropical connection along the Atlantic coast

Along with Beryl's impacts, new tropical moisture along the Atlantic coast will fuel bursts of rain that can lead to flash flooding, especially along much of the Interstate 95 corridor, late this week and into the weekend.

A ribbon of tropical downpours will occur along the western edge of high pressure near Bermuda. This downpour zone will crescendo into Friday before diminishing and exiting slowly on Saturday.

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The initial zone of downpours focused on coastal areas of the Carolinas and southeastern Virginia into Thursday afternoon, with some extending southward to Florida and northward to Delmarva.

"Holding off the downpours farther north over the mid-Atlantic and New England will be a press of drier air on the back side of Beryl," AccuWeather Senior Meteorologist Dave Dombeck said.

People from the central Appalachians to the I-95 metro areas of New York City, Philadelphia, Boston and Washington, D.C., got to experience lower humidity levels on Thursday, following days of extremely moist air.

But that drying trend will be interrupted and reversed.

Humidity levels will rise again late Thursday night to Friday night, which will pave the way for downpours in the Carolinas to expand northward into the mid-Atlantic and southern New England on Friday, Dombek explained.

Intertwined with the downpours will be a tropical low-pressure area that will be forced to the Carolina coast on Friday then ride northward along the mid-Atlantic coast Friday night and then the southern New England coast on Saturday.

The chance of the low-pressure area to develop into a tropical depression or named tropical storm before it reaches the coast at the end of the week is currently low. However, AccuWeather meteorologists will be closely monitoring the system as it will enter the very warm waters of the Gulf Stream.

Regardless of development, it will further enhance downpours along the Atlantic coast, AccuWeather Meteorologist Joseph Bauer said. The risk of development may continue to extend farther to the north along the Atlantic coast since the system will likely fail to move well inland.

A general 1-2 inches of rain will fall without the tropical low's influence, but where it becomes involved, local amounts of 6-8 inches can occur in 24 hours or less. Motorists should expect slowdowns on the highways due to torrential downpours and ponding in some cases on Friday and Friday night along the mid-Atlantic coast, back to portions of I-95. Street flooding can occur where the heaviest downpours linger for a couple of hours.

Because of this system's proximity to the coast, it can create a period of windy conditions and roughen up the surf. As is sometimes the case with even weak tropical systems, they sometimes trigger severe thunderstorms and waterspouts. Where rain falls much of the day on Friday, daytime temperatures will range from the mid-70s to the mid-80s F.

By Saturday, the low-pressure area will cross southern New England and then move out to sea. In the wake of this system, the rain will end, and humidity levels are likely to lower a bit once again.

A busy pattern next week will result in pockets of showers and thunderstorms in the Eastern states with one or more large complexes of thunderstorms from the Midwest rolling in. At the same time, temperature and humidity levels will build. Widespread highs in the 90s are forecast for much of next week with thunderstorms only offering temporary relief, where they occur.

Rain is needed for many in East

Any non-flooding rainfall would be welcomed in the mid-Atlantic, Piedmont and central and southern Appalachians, where drought conditions continue to expand. However, much of Beryl’s rain will hug the northern tier, and the coastal downpours will not reach well inland.

For one example of many, the Lynchburg, Virginia, area has received only 0.62 of an inch of rain since June 1, compared to a historical average of nearly 5 inches.

The sun’s intensity at this time of year evaporates a considerable amount of moisture from the topsoil daily. The lack of rain during this typically hot and high-moisture-demand time of year affects agriculture from parts of Georgia and Alabama to Maryland, southern Pennsylvania and New Jersey.

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