Helene, which brought catastrophic flooding to the Southern Appalachians, caused at least 40 deaths and cut power to more than 4 million customers, is no longer the powerhouse it was, but it’s still predicted to produce heavy rain and areas of flooding into early next week.

The system, now designated “post tropical,” will linger over the Tennessee Valley until Tuesday. That will keep showers and thunderstorms in the forecast there and in the Mid-Atlantic, though the National Weather Service deems the remaining flood threat to be comparatively “marginal.”

“Heavy intensity and accumulations are not expected to be widespread or heavy, however the recent wet period keeps an elevated threat for excessive rainfall and isolated flooding concerns,” the agency wrote.

Meanwhile, serious, life-threatening flooding continues across hard-hit areas in the Southern Appalachians because of runoff and scores of rivers that are above flood stage and have yet to crest. At one point, 18 flash flood emergencies — the most dire flood alerts, which indicate an immediate life-or-death situation — were in effect simultaneously.

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The storm’s devastating intensity — fueled by record-warm waters in the Gulf of Mexico — was probably increased by human-caused climate change.

And hurricane season is far from done. On average, 25 percent of a season’s activity comes after Sept. 28. Not only that, but there are indications that this season could be a “backloaded” one, meaning even more storminess ahead.

Forecasters are carefully watching the potential for another named storm to develop in the Gulf of Mexico next week.

What’s next for Helene

Helene merged with an upper-level low, or a high-altitude pocket of cold air, low pressure and spin. Their combined circulations, which have morphed into a midlatitude rainstorm, are still slinging showers in the forecast over Kentucky, southern Indiana and Ohio.

A small piece of good news comes in the form of “occlusion.” Explained simply, a wedge of dry air has wrapped all the way around Helene’s remnant low pressure system. That has cut off its moisture umbilical cord of sorts, meaning it no longer is being nourished by Gulf of Mexico moisture. Eventually, the low pressure system will dry up.

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That’s why rainfall intensity is waning and the flood risk has plateaued. But another half-inch to an inch are expected across parts of the Ohio and Tennessee valleys. Near the Ohio River, 2 to 3 inches are possible into Monday.

Looking back at Helene

Peak rain

Extreme rainfall brought widespread destructive and locally catastrophic flooding that left entire neighborhoods and communities underwater, particularly in the Southern Appalachians. Some areas saw 4 to 5 months’ worth of rain in just a few days. The peak total in western North Carolina logged by the Weather Service was 29.58 inches in Busick, about 24 miles northeast of Asheville.

Totals of 15 to 20 inches were widespread in the mountains of western North Carolina and South Carolina, as well as northeast Georgia.

In these zones, the heavy rains came in two rounds. One was a “predecessor rain event,” or an episode of rain far removed from a tropical cyclone. On Wednesday, moisture streaming north ahead of Helene interacted with a frontal boundary draped across the mountains to produce serious rainfall. Then another batch of heavy rains came during the passage of Helene.

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The excessive rainfall elevated rivers to record levels. In Asheville, the Swannanoa River at Biltmore and the French Broad River shattered records that had stood for more than a century.

Here are some notable rainfall totals from population centers affected by the storm from Florida to Virginia:

Panama City, Fla.: 13.11 inches

Atlanta: 11.13 inches

Augusta, Ga.: 13.56 inches

Asheville, N.C.: 12.11 inches

Paducah, Ky.: 6 inches

Nashville: 4.46 inches

Roanoke: 4.17 inches

Peak winds

Peak winds with tropical cyclones are notoriously difficult to measure and communicate. A 140-mph Category 4 — Helene’s intensity at landfall — will almost certainly not yield any 140-mph wind reports. That 140-mph reading corresponds to an idealized wind speed at the core of a tropical cyclone’s right eyewall at an exposed location at the beach. Winds decay rapidly with distance inland.

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In Perry, Fla., a Doppler on Wheels measured winds gusting to 100 mph. A nearby station in Suwannee clocked a gust to 99 mph. But to the storm’s west, winds in Tallahassee gusted only to 67 mph. An eastward jog at the last minute spared the state capital from a greater impact.

What was particularly notable is that 90-to-100-mph gusts made it all the way into southern Georgia. In Lowndes County, on the Florida border, winds gusted to 96 mph, and in nearby Echols County to 90 mph.

Winds in Douglas, in south-central Georgia, gusted to 92 mph. Macon and Atlanta were fortunate to escape with gusts of 48 and 43 mph respectively, but gusts in Augusta reached 72 mph.

Even into South Carolina, the winds remained strong. In Columbia, they gusted to 61 mph. And while there were some 80-plus-mph gusts recorded in the high elevations of the Carolinas, the lower elevations primarily stayed in the 50-to-60-mph range.

Storm surge also lived up to forecasts, with a confirmed, record-setting surge of 10.3 feet in Cedar Key, Fla. The National Hurricane Center also estimated that Steinhatchee, Keaton Beach and Horseshoe Beach — all small communities in the Big Bend — exhibited damage commensurate with a 15-foot or greater storm surge.

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That means the water rose 15 feet above ordinarily dry ground; 15 feet is the equivalent of a second-story window.

In the Tampa area, record surge caused significant damage. Clearwater Beach had a surge of 7.3 feet, exceeding the 6.76 feet observed during the “Storm of the Century” in March 1993. Tampa had a surge of 7.8 feet, surpassing the previous record of 7.24 feet set on Aug. 30, 2023. And Port Manatee had a nearly 6.4-foot surge, beating the record of 5.86 feet, also set in 2023.

Also of note with regard to Helene:

It is the fourth and strongest hurricane to make landfall in the United States this year (following Beryl, Debby and Francine)

It is the first hurricane on record rated Category 4 or higher to strike the Big Bend area

It is the fifth hurricane to hit Florida since 2022

It is the ninth major hurricane rated Category 3 or higher to make landfall along the U.S. Gulf Coast since 2017.

What forecasters are watching in the tropics

Meanwhile, there’s more in the tropics. The National Hurricane Center is monitoring the western Caribbean and southern and western Gulf of Mexico, where a tropical depression could form toward the middle of next week. Early indications suggest there is a reasonable chance it will become a named storm that could eventually threaten the gulf coasts of either the United States or Mexico. For now, the Hurricane Center gives the system a 40 percent chance of development in the next seven days.

Otherwise, Isaac is a hurricane over the north-central Atlantic. It will transition into a nontropical cyclone and drift northward over the open ocean.

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Joyce is a tropical storm about 1,165 miles east-northeast of the northern Leeward Islands. It’s slowly meandering west-northwest as a tropical storm and will eventually weaken. No impact to land is expected.

And then there’s another system to watch midway between the Lesser Antilles and Africa. It has a medium chance of development.

The next two systems to earn names in the tropical Atlantic will be called Kirk and Leslie.

Despite Helene’s powerful wrath in the Gulf of Mexico, the total amount of accumulated energy from Atlantic tropical systems this year is still running slightly below normal because of the long pause in storm activity between mid-August and mid-September. However, there are some early signals that October could be a rather busy month in the Atlantic.