Weather Outside Your Window: Slight pattern change won't bring widespread cooldown to Northeast

By Alex Sosnowski, AccuWeather senior meteorologist

Updated Aug. 25, 2021 12:31 PM EDT

AccuWeather forecasters expect some relief from prolonged heat and humidity to take hold across the Northeast this weekend, but it won't be a massive fall preview for areas from Virginia to Pennsylvania.

Hot and humid conditions that expanded in the wake of Henri early this week will linger in most areas through Friday. That means more high temperatures ranging from the upper 80s to the middle 90s F, with AccuWeather RealFeel® Temperatures ranging from the 90s to low 100s.

There are some changes coming to New England this weekend, but people in the mid-Atlantic hoping for a blast of cool, refreshing air similar to mid- to late-September and October will be greatly disappointed, according to AccuWeather Senior Meteorologist Brett Anderson.

It is tough for cold fronts to reach much of the Atlantic coast during August, and that will be the case in the coming days.

"For a front to roll through with a major change to cool weather, there needs to be a significant southward dip in the jet stream to help nudge the Bermuda High out of the way. Instead, the jet stream will barely have a ripple this weekend, so the air aloft will remain quite warm," Anderson explained.

There will be some cooling in the lower part of the atmosphere that will be assisted by the Atlantic Ocean.

Water temperatures are about their highest levels of the year right now, ranging from the 60s along the coast of Maine to the lower 80s along the Virginia capes.

"Any cooling by way of a northeasterly or easterly breeze will be limited and will tend to carry some moisture along with it," Anderson said.

Some reduction in humidity is likely for New England and part of upstate New York, but the humidity drop may become progressively less noticeable farther to the south and west this weekend, due to the ocean adding its moisture contribution to the air.

"It is possible for no significant change in humidity to occur from New York City on south and west this weekend," Anderson said.

CLICK HERE FOR THE FREE ACCUWEATHER APP

High temperatures are forecast to take a bit of a hit, especially in New England and northeastern New York state, where highs are forecast to trend downward to the 70s and even the upper 60s.

Some of the best weather this weekend in terms of low humidity sunshine, and fall-like conditions may be in Maine, closer to the source of the cool and dry air from eastern Canada. For example, high temperatures in Bangor, Maine, are forecast to trend from near 90 on Thursday to the lower 70s on Saturday and the upper 60s on Sunday. High temperatures at that level are more typical of mid- to late-September.

Farther to the south and west, the high temperature trend may only be 5-10 degrees lower from the extremes of much of this week. By Sunday, highs are forecast to range from the middle 80s in Pittsburgh and Philadelphia to just shy of 90 in Washington, D.C.

"Any time there is a flow of air partially or fully from the Atlantic, there can be issues due to cloud cover, lingering misty conditions and even patches of rain or thunderstorms. These are also concerns for this weekend in the mid-Atlantic, central Appalachians, Great Lakes and even New England," Anderson said.

During the summer, a change in air temperature, whether subtle or extreme, can also mean the risk of thunderstorm development. Some storms forecast to develop later this week could become locally heavy and possibly slow-moving, which could mean the risk of flash and urban-style flooding.

"For those heading to the beach this weekend, in addition to the potential for stubborn clouds and even some rain, a stiff breeze from the Atlantic may lead to rough surf and strong rip currents from the southern New England coast to Long Island, New York, New Jersey and Delaware," Anderson added.

Through Thursday night, the storm risk may be confined to the central Appalachians and eastern Great Lakes region. By the weekend, spotty storms may expand eastward to reach the mid-Atlantic and southern New England coasts.

Another potential concern at the beaches is that runoff from Henri's flooding on Sunday and Monday may have washed pollutants into the surf zones. People are urged to abide by any local restrictions set forth by officials due to weather or contaminants.

During the middle and latter part of next week, it may be possible for a more substantial push of cooler and less humid air to reach the central Appalachians and mid-Atlantic coast. However, potential developments in the tropical Atlantic, and the Gulf of Mexico in particular, may add some level of complexity to the forecast, should a system push northward into the Southern states.