Wet Labor Day to precede heavy rain, flooding in Northeast

September began with pleasant conditions across much of the Northeast, but a change to a more unsettled pattern arrived just in time to spoil Labor Day weekend plans for some. AccuWeather meteorologists caution that much more wet weather is ahead, including the possibility of heavy rain and localized flooding in parts of the Northeast.

The culprit for the wetter weather is a front that continues to slide eastward, albeit at a slow pace. Meanwhile, an area of low pressure is expected to form along this front, enhancing the intensity of the rainfall.

"The slow movement of the area of low pressure will allow the system to efficiently pull moisture from the Gulf of Mexico and Atlantic Ocean northward and into the Northeast beginning on Monday," AccuWeather Meteorologist Joe Bauer explained.

Unlike the spotty nature of rain and thunderstorms Sunday, Monday's rain and storms should be much more widespread across the region. However, a few breaks in the rain are possible throughout Monday, providing windows of opportunity for folks who are looking to spend at least part of Labor Day outdoors without an umbrella.

Some of the heaviest rain will begin Monday night. With the slowness of the approaching front combined with the rich moisture being pulled into the Northeast, the stage will be set for intense rain to move over the same areas repeatedly. Repeated rounds of rain and thunderstorms can cause rainfall totals to approach monthly averages in just a few hours. This weather setup is a process known as "training."

"Despite the Northeast having some dry areas at times, the rain moving into the region can become heavy enough to produce localized flooding as heavier clusters of storms develop," AccuWeather Senior Meteorologist Matt Rinde explained.

Many of the major Northeast cities could experience flooding into Tuesday due to the anticipated rainfall. As of Monday morning, flood watches were in effect from Alabama to Maine, including Atlanta, Cincinnati, Pittsburgh, Philadelphia, New York City and Boston.

Some of the highest chances of flooding will occur in urban areas, where vast amounts of non-porous surfaces such as pavement and roofs do not allow for water to soak in, which can lead to quickly rising water levels. The mountainous and hilly terrain is also highly susceptible, as runoff can flow into narrow valleys and streams.

Flooding due to this system has already proven to be impactful elsewhere with 9.40 inches of rain falling in Pleasant, Indiana, located about 80 miles southeast of Indianapolis. Typically, this area of southeastern Indiana receives between 3 and 3.5 inches of rain in all of September.

Rainfall totals as of early Monday morning.

At least one person was killed in southeastern Indiana on Saturday as flash flooding swept away several homes.

By Wednesday, the area of rain should become more spotty and push southward, beginning a drying trend in the Northeast. By the second half of the week, a return to dry, seasonable and calm weather will take place across the region.