Soggy conditions return to the Northeast

After a dry start to the month, a wet pattern is in store for residents from the Ohio Valley to New England coast this week.

Now that the calendar has officially crossed into astronomical autumn and leaves have started to gain their vibrant colors and fall to the ground, Mother Nature will usher in a notable pattern change across portions of the Northeast.

While the start of meteorological fall is always the first of September, the first day of astronomical fall changes from year to year, and depends on when the sun shines directly on the Equator. This year, the fall equinox was on Sept. 22, at 8:43 a.m. ET.

Slightly cooler conditions, rounds of rain and showers and even thunderstorms will be the theme from the Ohio Valley to parts of Pennsylvania, New York and the mid-Atlantic states, at least for the first half of the week.

A slow-moving storm spanning from southeastern Canada to parts of the Tennessee Valley has kicked off the damp workweek, but it will be quickly followed up with a separate storm chugging directly behind it.

This will lead to several days featuring rounds of wet weather from parts of the Midwest to mid-Atlantic states, with travel concerns possible.

From late last week into the start of the weekend, a coastal storm brought plenty of rain to portions of far southeastern New England, especially along the Cape and Islands region of southeastern Massachusetts.

Over 5 inches of rain fell on Nantucket from Thursday through Saturday, bringing that area well above its historical average month-to-date rainfall through Sept. 21. There was a sharp gradient of rain totals, however, and the total rain for Boston remains at only 36% of the historical average.

Storms, some severe, on the way for drought-stricken areas

Cities such as Columbus, Ohio, have been parched so far this September, only picking up around 4% of the typical September rainfall through Sep. 23. Even dating back to the start of June, the city has only collected around 34% of the typical rainfall.

Levels of exceptional drought are still being observed across portions of West Virginia and southern Ohio, but AccuWeather forecasters highlight that this week may provide some much-needed relief for the prolonged dry pattern.

Into Tuesday evening, robust storms can develop as energy transitions through the Ohio and Tennessee Valleys. Localized damaging wind gusts from 55-65 mph can occur within the strongest storms, paired with flooding downpours.

Through at least midweek, rounds of rain and thunderstorms will result in 1-3 inches of rain across the Ohio Valley and mid-Atlantic states. However, this will come at the risk of nuisance flooding, especially where leaves have already begun to fall. The heavy rain and fallen leaves clog storm drains, which can lead to ponding on roadways and slick travel conditions.

Even for locations farther east, such as Philadelphia and New York City, substantial rain has not been observed throughout the month of September, both standing at or below 10% of the historical average monthly rainfall.

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The prolonged dry stretch in New York City finally came to an end on Monday, with the Big Apple picking up 0.04 of an inch of rain, marking the highest single-day rainfall there since September 7. Still, New York has had only 0.28 of an inch of precipitation this month, well below the month-to-date historical average of 3.28 inches through Sep. 23.

"As a slow-moving storm moves out of the Great Lakes and into the Northeast and mid-Atlantic later this week, moisture will be drawn northward and this will finally bring the dry stretch to an end. Currently, New York City could see at least 0.25-0.50 of an inch of rainfall during the midweek period, with the potential for more later in the week if tropical moisture is drawn northward from the Gulf of Mexico," noted Pydynowski.

AccuWeather meteorologists expect a major hurricane to form in the Gulf of Mexico by midweek and strike along the northeastern Gulf coast prior to the end of the week.

Temperatures comparable to early-October

Not only will the weather pattern turn wetter this week across the Northeast, it will also trend cooler. Temperatures will transition from the 80s Fahrenheit observed at times last week to the the 70s and 60s F this week.

By midweek, highs in New York City will dip into the upper 60s F, closer to typical values observed in early October rather than late-September temperature. While many might welcome the cooler conditions and stretch of wet weather after such a dry month so far, it could also cause headaches for certain outdoor events this week.

"The potential for rain around midweek could cause delays in a key baseball game Wednesday evening as the New York Yankees host the Baltimore Orioles in the Bronx, New York, in an important series," noted Pydynowski.

Chilly and wet conditions can linger into Thursday night, just in time for the football game between the Dallas Cowboys and the New York Giants in East Rutherford, New Jersey.

Looking ahead to late week

As the week continues, the prospects for rain and showers will transition eastward into New England and the mid-Atlantic coastline, dampening locations across Vermont, New Hampshire, Massachusetts and eventually Maine.

Conditions will trend drier across areas of the Great Lakes and Upper Ohio Valley, but how long the return of dry weather continues will depend upon the movement of a few features AccuWeather meteorologists are monitoring-- such as the storm that is likely to become Major Hurricane Helene.

"There is some risk that the eventual Helene will throw some moisture northward to give quite a wet late-week period to the East Coast, but this is currently not the favored outcome, as it may end up more likely that another storm over the Mississippi Valley can capture the eventual tropical feature and pull its moisture in that direction instead," AccuWeather Meteorologist La Troy Thornton explained.

Depending on the track of this feature, rounds of moisture can return to the Tennessee and Ohio Valleys later this week, or it could be swept to the east and travel off the Southeast coast. Residents are urged to continue to check back to AccuWeather.com for the latest insights on where this storm is projected to travel.

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