Northeast at Risk of Flash Flooding as Stream of Moisture Kicks Up

While relief from the searing heat is on the way for the Northeast, it will come at a cost. Along with the cooler temperatures will come a surge of moisture that will raise the threat of flash flooding across the region. Here is what you need to know about this developing situation.

Flash Flooding Risk Across the Northeast in Days Ahead

It could be a soggy stretch of weather for many areas of the Northeast. Torrential downpours and the chance of severe weather will roam this corner of the country through Friday. Some communities could pick up several inches of rain out of the weather maker, creating the risk of flash flooding.

The Northeast has already seen a wet summer with the rain arriving in spurts over the last few months. The latest influx of precipitation will come as an advancing cool front pairs with a ripple in the jet stream to produce the heavy rain well into Friday. This combination of atmospheric elements will also impact the Southeast into the early part of next week.

The initial bands of heavy rain are moving in from the Midwest after dousing parts of the central U.S. on Wednesday. The line of moisture is expected to move from northern Indiana and southern Michigan to the east into the northern tier of Ohio, northwestern Pennsylvania, and the southwestern corner of New York through the early part of Thursday.

The Northeast should also prepare for the chance of severe storms on Thursday morning. While the storm action will not be as widespread as some of the weather that has impacted the region in recent weeks, they are still a threat to take seriously.

The greatest risk of flash flooding will set up across the mid-Atlantic region and to the north into southern New England. This is the general area where the cool front and the dip in the jet stream will converge to generate the repeated rounds of rainfall.

Widespread rainfall accumulations of 2 to 4 inches are expected for eastern Pennsylvania, northeastern Maryland, northern Delaware, Connecticut, and the lower Hudson Valley of New York. This includes the populated area in and around New York City.

Rainfall of this magnitude is capable of overwhelming storm drains in a short matter of time. Travel disruptions on the roads and in the skies are likely on Thursday evening and again on Friday morning.

Forecasters are warning that some of the most potent storm cells could usher in strong wind gusts at times. The highest winds are expected on Friday in a zone from the Carolinas and to the north into southeastern Pennsylvania and southern New Jersey.

Specific Local Forecasts

Looking at a few of the local forecasts in the impact zone, Philadelphia will wake up to partly cloudy skies in the morning, with storms developing in the afternoon. The City of Brotherly Love will see one more day of heat with a forecast high of about 90 degrees. The overnight forecast is calling for more locally heavy rainfall and a low of about 66 degrees. Winds will also pick up at this time, reaching speeds of 10 to 15 mph from the north-northeast.

Friday will usher in drier conditions in Philadelphia. However, you cannot rule out the threat of a stray rain shower. The mercury will top out in the mid 70s with lows expected to slip to about 63 degrees.

Washington, D.C. will also be under the gun for times of heavy rainfall throughout the day and night on Thursday. The nation's capital is expecting a high of 90 degrees on Saturday before the cool front moves in and knocks down the temperatures. Friday's high will struggle to climb out of the mid 70s with lows that dip into the mid 60s. Wind speeds will also pick up slightly overnight Thursday and into Friday, reaching 10 to 15 mph.

It will be even soggier to the north in Boston. Bean Town is bracing for about a half of an inch of rain during the day and another inch of rain tacked on overnight. The cooler air will dive down into this region earlier, translating to a high of just 74 degrees on Thursday. Despite the arrival of some sunshine late in the day on Friday, highs will max out in the upper 60s in this part of New England. It will be a breezy day in Boston, with winds clocking in at 10 to 20 mph from the northeast.

The rain will take longer to depart the coastal regions. For instance, Atlantic City, New Jersey, is expecting rainfall of about an inch overnight on Thursday. The steady stream of moisture will persist on Friday in the beach town with the possibility of heavy rainfall. Winds will also be more intense in this area, coming in at speeds of 20 to 30 mph from the north-northeast.

Atlantic City is forecast to see highs in the mid 80s on Thursday, plunge to about 73 degrees on Saturday. Overnight lows will land at about the 70-degree barrier on Thursday before sliding farther into the mid 60s on Friday night.

Lovely Weekend Weather in Store for the Northeast

The bulk of the worst weather in the eastern U.S. over the weekend will migrate to the Southeast. This movement will translate to largely pleasant conditions for the Northeast, particularly when compared to typical early August standards. The strain on energy systems will ease, especially in the overnight hours when the mercury falls noticeably

The lovely weather will come as a high-pressure system over central Canada dips to the south. Typical highs this time of the year hover in the 80s and the low 90s. Overnight readings generally land in the 60s and low 70s. The intrusion of cooler air from the north will keep highs in the 60s in the higher elevations of the Northeast and the low 80s along the Interstate 95 corridor and in the mid-Atlantic.

Overnight lows will slip into the 40s in the mountains, making for some chilly nights in some of the most popular summer vacation spots in the region. A few isolated areas may even see the temperatures fall as low as the upper 30s. The major cities in the Northeast should expect overnight lows in the 60s.

Going back to Philadelphia, the largest metro area in Pennsylvania, will enjoy temperatures that bounce around in the low to mid 80s for highs on both Saturday and Sunday. Mostly sunny skies will make it a good time to head outside for summer fun.

High temperatures will remain in the mid 70s on Saturday in Boston before creeping back into the low 80s to close out the weekend. The forecast is calling for mostly sunny skies and overnight lows that dip just below the 60-degree threshold.

It will be a great weekend to check out the monuments along the National Mall in Washington, D.C. Tourists can expect plentiful sunshine and highs in the low 80s for both days. Take a jacket if headed out for a nighttime tour of the sights, as lows will drop into the low 60s after the sun goes down.

The change will also bring down the humidity levels. This may be the most noticeable impact of this shift in the conditions. You can also expect breezes to pick up across coastal portions of New England and the mid-Atlantic over the weekend. The breezes will come as a result of the clash of the high pressure to the north and the storms firing up to the south.

The steady winds will also create rough surf conditions and a greater threat of dangerous rip currents. The stubborn onshore breezes could send water levels up to 2 feet over the norm, generating minor flooding during times of high tide.

Looking ahead to next week, the zone of high pressure will slowly begin to lose its grip over the Northeast. The forecast for Monday and Tuesday is looking promising for outdoor activities; however, heat is likely to build again by the latter half of the week.

We will continue to monitor the forecast models for next week and keep you updated in the days ahead.

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