Risk of flooding downpours continue in the northeastern US through early this week

By Alex Sosnowski, AccuWeather senior meteorologist
August 12, 2018, 6:55:13 PM EDT

Drenching showers and thunderstorms will bring the risk of flash flooding to the central Appalachians and parts of the mid-Atlantic into early this week, while the heaviest rain may focus on parts of New England.

Have the umbrellas and raincoats handy again. There is the potential for the wettest swath in the Northeast to receive 5 inches of rain with locally higher amounts before the pattern breaks up.

Whether 5 inches of rain falls in as many days or an inch of rain falls in an hour, enough rain is expected to fall to lead to rising streams and possible urban and small stream flooding.

Repeating storms wasted no time in hammering parts of Ohio and southwestern Pennsylvania. More than 3 inches of rain fell on some of the suburbs of Pittsburgh in several hours on Friday afternoon.

More than 5 inches of rain fell in just a few hours in the town of Lynn, north of Boston, which flooded roadways and stranded cars.

"The greatest risk of flash flooding will be during, but not limited to, the daytime and early evening hours," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.

For the latest on the location of downpours and the risk of flooding in your area, download the free AccuWeather app.

NEintoTues 8.12

The rain may lead to delays and cancellations of some sporting events and could make moving into a new home, apartment or dorm quite difficult.

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The swath of heaviest rain is likely to extend from parts of eastern Pennsylvania and New Jersey through the Hudson Valley, and into much of southern New England.

A second pocket of heavy rainfall may extend from southeastern Virginia to the coastal areas of the Carolinas into Tuesday.

The setup is likely to have more success at bringing downpours to the mid-Atlantic and southern New England beaches when compared to July. People heading to the beach for a last summer getaway before school starts may have to dodge some showers.

Areas most likely to escape the most persistent rainfall are from central and northern Maine to northern New York state and Michigan as well as portions of Ohio.

However, most locations in the Northeast, even those outside of the most persistent rainfall, will still run the risk of a downpour that could lead to isolated urban flooding.

A number of locations experienced their wettest July on record in the mid-Atlantic states including Harrisburg, State College and Williamsport, Pennsylvania; Baltimore and Washington, D.C.

Static AP Tremont PA

A volunteer hauls a hose past flooded homes as he and others helped pump water out of basements on Wednesday, July 25, 2018, in Tremont, Pennsylvania. Days of drenching rains closed roads, sent streams over their banks and prompted some evacuations in central Pennsylvania. (AP Photo/Jacqueline Larma)

Flooding forced evacuations and closed amusement parks in the region during the peak of the summer season.

Both Hartford, Connecticut, and New York City have received close to 10 inches of rain since early July. This rainfall is 150 to 200 percent of normal.

Meanwhile, portions of northern New York state and northern New England are experiencing moderate drought. In parts of this area, rainfall since July 1 has been only 50 percent of average.

What is causing the latest round of wet weather?

Just like the rainy patterns experienced in July and early August, the weather pattern set to produce the wet weather will not be correlated with a tropical storm.

A non-tropical storm is forecast to form and stall over the central Appalachians this weekend into early next week.

Even though the center of this storm will be located near the jet stream level of the atmosphere, the circulation around this storm will be able to pump a substantial amount of moisture in from the Atlantic Ocean and the Gulf of Mexico, Pastelok stated.

"We don't expect the troublesome upper-level storm to move out until later Tuesday or Wednesday," Pastelok said.

More wet weather may be in the offing later in August

A break in the frequent downpours is likely for the middle part of next week, but another slow-moving storm in the upper atmosphere may return by next weekend with more rounds of showers and thunderstorms.

Since the pattern is looking more likely to remain wet through August, there may be a heightened concern for significant flooding as the hurricane season peaks during September and early October.

It would not take a powerful hurricane to cause major river flooding, but a mere slow-moving tropical storm tracking through the region could be enough.

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