Cooler, less humid air coming to Northeast, but issues remain in Debby's wake

While many rivers continue to rise this weekend in the wake of Debby, AccuWeather meteorologists say that a push of cool, dry air from Canada will spread from the Midwest to the central Appalachians, mid-Atlantic and New England.

The change will be welcomed by millions who have been dealing with everything from tropical humidity and flooded basements to difficult travel and spoiled outdoor plans. Many people will be able to turn off their fans and air conditioners, significantly reducing energy demands in the region.

Daytime highs over the upper Great Lakes region will be in the 60s F through the end of the weekend, and some of that cool air will spread toward the Ohio Valley and Northeast.

"This is really cool air for August, and with the Great Lakes being quite warm, it is a perfect recipe for waterspouts to form," AccuWeather Meteorologist Brandon Buckingham said.

The lake effect will also lead to clouds, spotty showers and even thundershowers in parts of the Great Lakes region, but the air will feel quite cool and not tropical like it has been in the Northeast.

Chicago and Detroit's highs this weekend will be mainly in the 70s. Highs in the Northeast's Interstate 95 corridor, including Boston, New York City, Philadelphia and Washington, D.C., will trend downward through the 80s.

Temperatures in the central and northern Appalachians will drop into the 50s by Saturday night, and some cool-sensitive people may have to shut the windows to keep chilly air from entering their homes.

Through Saturday evening, humidity levels will drop east of the Appalachians, setting the stage for cool nights and mornings from Saturday night to well into next week, with lows mainly in the 60s.

The drying conditions will be interrupted by lake-effect showers as far to the south and east as northern Ohio, northern and western Pennsylvania and northwestern New England as well as western, central and northern New York this weekend.

Farther west, batches of showers and thunderstorms will ride the rim of the heat from the central and northern Plains to the Ohio Valley and perhaps parts of the central Appalachians and mid-Atlantic next week.

Meanwhile, in the wake of Debby, so much rain was unloaded on areas from Georgia and the Carolinas to Pennsylvania, New York and New England that many rivers are experiencing moderate to major flooding. It will take a few days for rivers to crest well inland, but it could take a week or more for rivers in lowland areas of Georgia and the Carolinas to crest and a couple more weeks to drop below flood stage.

This is why AccuWeather meteorologists call river flooding a slow-moving disaster that lingers well after the last raindrops have fallen.

Along with ongoing river flooding concerns, water will linger where it has collected in poor-drainage areas.

Where humid air lingers in the central and eastern Carolinas to much of Georgia, more showers and thunderstorms are likely to erupt this weekend.

"These storms will be slow-moving and tend to repeat over some of the same areas that were hit hard by flash flooding and experiencing ongoing river flooding," AccuWeather Senior Meteorologist Matt Benz said, "Because of this, the downpours could aggravate flooding problems."

There is another concern for those heading to the beaches in the wake of Debby.

"Quite often following a heavy rain event, deposits that work into coastal waters can bring pollutants and trigger bacteria blooms along some beaches," AccuWeather Senior Meteorologist Brett Anderson said.

Swimmers are urged to obey local ordinances that may cause some beach closures this weekend.

A new threat from the tropics may arise late next week. AccuWeather meteorologists are tracking a new feature over the south-central Atlantic that is likely to become the season's next tropical storm and perhaps a hurricane. Steering breezes could guide that feature close to the East Coast of the United States next weekend.