Persistent wet weather to extend flooding risk in Northeast as rainfall records rack up

By Alex Sosnowski, AccuWeather senior meteorologist
August 16, 2018, 8:21:42 AM EDT

Persistent rainfall and flooding are likely in parts of the northeastern United States that have already received record-shattering rainfall this summer.

"The weather pattern this summer is one of the most dramatic outbreaks of rain ever to hit Pennsylvania and other states in the region in a non-tropical storm setting," according to AccuWeather Chief Meteorologist Elliot Abrams.

Static 30-Day Rainfall

The recent deluge has been on par with the type of rainfall that can be unleashed by a tropical storm or hurricane.

For example, at Wilkes-Barre/Scranton International Airport, Pennsylvania, 4.34 inches of rain fell on Aug. 13, which shattered the old record for the date set in 1955. The location received more rain in one day than what typically falls for the entire month of August.

static NE rain infogram 8.15

The 1955 rainfall was directly related to Hurricane Connie. That tropical system tracked northwestward across Pennsylvania and was later followed by Hurricane Diane and catastrophic flooding in the Delaware Valley later in August.

Some locations have already recorded their wettest summer on record, such as State College, Pennsylvania.

Williamsport, Pennsylvania, is likely to have two back-to-back months of record rainfall. Following the wettest July on record, the wettest August on record is on the doorstep.

The downpours have been triggered by frequent storms as well as tropical moisture funneling into the area from the Gulf of Mexico and the Atlantic Ocean, according to AccuWeather Hurricane Expert Dan Kottlowski.

A persistent area of high pressure off the Atlantic coast is helping to direct the fire hose of moisture.

What lies ahead for the Northeast?

On Thursday, the lull in shower and thunderstorm activity will continue in the mid-Atlantic and spread to New England. However, even with the lull, spotty pop-up downpours are still expected.

Areas most likely to be hit with a downpour later in in the day or during Thursday night will be along the western slopes of the Appalachians.

During Friday, another storm will push in from the Midwest.

Static Rain Friday

Showers and thunderstorms, some with enough rain to renew or bring flash flooding to areas that have escaped thus far, will spread slowly eastward.

The heaviest total rainfall may fall across northern New York state and New England this time. However, portions of the Atlantic seaboard could still be hit hard.

"A great amount of moisture will be available in the atmosphere on Friday along the Interstate-95 corridor," according to AccuWeather Senior Meteorologist Bernie Rayno.

There is a bit of good news with this latest storm to affect the region. A batch of dry air is forecast to punch eastward across hardest hit flood areas of Pennsylvania, New York state and New Jersey by Sunday.

There is the potential for showers and thunderstorms to linger farther south across portions of West Virginia, Virginia and Maryland through this weekend.

Static US Weekend

While flash flooding can occur anywhere in the pattern, these more southern locations can stand a bit more rain, when compared to areas farther north over the Appalachians and mid-Atlantic region.

Another lull in the pattern is likely early next week.

However, yet another storm is forecast to push eastward during the middle part of next week.

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There is the potential for next week's storm to stall and create another flash flood concern.

On the other hand, if this storm manages to move swiftly through, it may be a "one and done" scenario as far as a shower or thunderstorm is concerned.

AccuWeather meteorologists are concerned the slow-moving storm scenario may win out as that scenario has occurred multiple times this summer.

Static Rain Next Week 3 pm

Either way, there is a risk of downpours that can lead to renewed flooding problems. A slow-moving storm would mean more widespread flooding. A fast-moving storm may mean more localized problems from flooding, but could also correspond to thunderstorms with brief downpours and gusty winds.

Flood risk may continue beyond the summer

Even though a lower-than-average count of hurricanes and tropical storms is foreseen, due to a developing El Niño, there is still the risk of a tropical system with direct impact in the eastern United States this autumn.

Well into the autumn, river, small stream, lake and reservoir levels are likely to remain above average in a large part of the Eastern states, with the possible exception of parts of New England and northeastern New York state.

Local, state and federal officials should remain vigilant well beyond the short-term issues.

Given the saturated state of the ground, declining evaporation rates and no sign of prolonged dry weather, any tropical system that comes calling could lead to a regional flooding disaster.

Likewise with the saturated ground, any gusty thunderstorm, let alone a tropical storm, can topple scores of trees and lead to regional power outages.

Download the free AccuWeather app to stay aware of flooding dangers.

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