100-degree heat dome to set up shop over southern US

The heart of summer is here and a major pattern change unfolding in the coming days will yield searing heat for millions over the southern United States, centered over the Plains and Mississippi Valley, Accuweather meteorologists advise. The same pattern, caused by a massive area of high pressure, will limit heat and high humidity to a handful of days in the Northeast.

Many locations that have avoided 100-degree heat thus far will rack up a string of triple digits in the days ahead.

In Wichita Falls, Texas, located about 100 miles northwest of Dallas, the average date of the first 100-degree reading is June 10. As of Friday, July 18, the hottest it has been was 98 on July 17.

A northward bulge in the jet stream will develop while high pressure builds. This setup-a heat dome-can be very persistent. While the core of the heat dome may meander east-to-west and back in the weeks ahead, it may linger through a good chunk of August.

Dallas, which as of July 17 had not hit triple digits, could do so on any of the days over the next two to three weeks. The pattern will erase the below historical average temperature condition thus far in July (1.5 degrees below normal) and is likely to finish the month near to above the historical average.

“Kansas City, Missouri, has not hit 100 degrees since Aug. 25, 2023, but is positioned to do so on multiple days during the upcoming heat dome,” AccuWeather Senior Meteorologist Chad Merrill said.

The heat will make it difficult for manual labor jobs ranging from construction to agriculture, as well as the start of athletic training camps for the upcoming start of the school year. Caution is advised to take breaks and stay hydrated.

It will take a while for the ground to dry out in some areas and, as that moisture is drawn into the air, it will make for very muggy, steamy conditions for a time, Merrill said. “Many cities over the South Central states won’t get relief at night with low temperatures to range from the mid-70s to the low 80s.”

“The zone from central Texas into the Ozarks in Arkansas and Missouri still has wet soil from recent rain,” Merrill added. “The humidity levels will end up highest in this area, leading to extremely muggy conditions next week. AccuWeather RealFeel® Temperatures will peak around 110 degrees next week in this zone.”

With the core of the heat dome centered over the southern Plains, it will be difficult for thunderstorms to occur.

“The bottom line is that this has the look of a long-lasting heat wave with limited rainfall,” Merrill said. “Drought will expand through the central Plains by mid-August and worsen in Kansas and Nebraska, where there are already pockets of moderate to extreme drought.”

As the ground dries out, temperatures will trend upward. Multiple days will have highs ranging from the mid-90s to the low 100s. In some areas, actual temperatures could even push 110 F as average soil moisture transitions to abnormally dry to drought conditions.

Some tropical moisture can push westward from the Gulf and into parts of central and southern Texas and spill northward from Mexico and into the Deserts, Rockies and High Plains in the form of periodic thunderstorms.

Pattern to bring rounds of cooler, less humid air to Northeast

As the heat dome builds and meanders over the Southern states, a large southward dip in the jet stream will develop and persist from the Upper Midwest to the Northeast.

This pattern will result in frequent fronts that bring extended bouts of cool and less humid air. Heat and humidity will surge ahead of the fronts, but likely only for a day or so here and there. In other words, the relentless sauna bath feel and torrential downpours leading to flash flooding should go away as the pattern evolves.

However, there can still be quick-moving severe thunderstorms with brief downpours and strong wind gusts. The pattern will be a guard against tropical storms from making a northward run along the Atlantic coast of the U.S., as any storm that forms would be shunted out to sea or directed westward across the Gulf.

A dose of cool air will visit the Northeast early next week following a bounce-back of humidity, downpours and thunderstorms on Sunday.

Heat will briefly surge back in later in the week in the Northeast. However, that heat is not expected to be of long duration and will likely be followed by an even more impressive surge of cooler and less humid air for next weekend.

Areas from the central and northern Plains to the Ohio Valley and Southeast will need to be on guard for long-traveling complexes of damaging thunderstorms, known as derechos, in the pattern.

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