Tropical downpours to douse US East Coast in wake of Beryl

The main thrust of Tropical Rainstorm Beryl's downpours beyond Wednesday focused 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.

Before its exit, the tropical rainstorm continued 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 fell 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 Wednesday night to Thursday 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 occurred, and much of the total rainfall from Beryl fell in six to eight hours," AccuWeather Meteorologist Alyssa Glenny said, "Hence the concern for flash flooding."

In the wake of 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 into the start of 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 night before diminishing and exiting slowly on Saturday.


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.

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. However, that drying trend reversed Thursday night.

AccuWeather Senior Meteorologist Dave Dombek explained that humidity levels will surge into Friday night, paving the way for prolific downpours in the Carolinas and southern New England.

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

It is highly unlikely that the low-pressure area will develop into a tropical depression. However, AccuWeather meteorologists will still monitor the system as it will be both close to the coast and near the warm waters of the Gulf Stream.

Even without development, it will further enhance downpours along the Atlantic coast and its circulation will tend to rough up the surf with locally strong and frequent rip currents into Saturday.

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 into Saturday morning 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.

On Saturday, the low-pressure area and downpour zone will retreat to the Atlantic slowly, but it may take until the evening or night before the corridor of moisture moves off most of the mid-Atlantic and New England coasts. There will also be pop-up showers and thunderstorms farther inland, especially in the central Appalachians and northern New England for the first day of the weekend.

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 from Sunday through Wednesday of next week with thunderstorms only offering temporary relief, where they occur.

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 hugged 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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