More than 50 million Americans are in line to experience temperatures above 100 degrees, and it’s likely heat advisories and excessive-heat watches and warnings will be issued as the event nears. It comes less than a week after much of the Southwest, the Plains and the Ohio and Tennessee valleys dealt with stifling heat and humidity.
It all stems from the same parent heat dome that has been languishing and refusing to budge from its perch over North America. It initially built into the Western United States. Its next act will feature an expansion and intensification of its sphere of influence, with the ridge of high pressure soon to sprawl across the entire Lower 48
The next big pulse of heat will be established Tuesday of next week and will really dominate from Wednesday onward. According to a plot produced by Tomer Burg, a graduate student in atmospheric sciences at the University of Oklahoma, temperatures at the 850 millibar level — roughly a mile up — will reach top-tier records in the skies over Alabama, Georgia and South Carolina. When it’s hot in the sky, it’s even toastier at the surface. That indicates decent chances of triple-digit heat.
“High temperatures alone (but more certainly heat indexes) Wednesday, Thursday, and Friday could necessitate Heat Advisories across portions of the area,” wrote the National Weather Service office in Peachtree City, Ga. The combination of highs pushing 100 degrees and Gulf humidity will make for heat indexes potentially nearing 110 degrees.
As for actual air temperatures, Atlanta is looking at a forecast of 98 degrees on Tuesday and 100 on Wednesday and Thursday. Macon could see highs around 102 or 103 degrees. In Macon, the temperatures could beat records of 101 degrees set in 1925 and 1988 on Wednesday and Thursday, respectively. Atlanta will likely topple daily records that have stood since World War II.
Nashville is predicted to see a high of 101 degrees on Tuesday and Wednesday — both likely topping records from 1988 — and a high of 100 degrees Thursday, which may fall a degree short of tying a record.
Dew points, meanwhile, will sit in the mid- to upper 60s along the Interstate 20 corridor and the lower 70s along Interstate 10, combining with the heat to yield heat indexes in the 105- to 110-degree-range. This could be especially problematic for low-income residents, the elderly and other vulnerable populations who may not have the means to escape the brutal heat.
On Friday, the ongoing heat across the eastern United States was beginning to pull back south a bit as a cold front collapsed toward the Gulf Coast. Heat advisories were still in effect for parts of the coastal Carolinas, the Deep South, the Ozarks and the central Plains, but alerts had been dropped over the Midwest and parts of the Tennessee Valley.
Heat advisories were issued in Montana ahead of the next pulse of anomalous heat, which is expected to bring highs in the upper 90s to near 100 degrees on Saturday. There’s a chance that Glasgow could nick 100 degrees; the average high this time of year is about 79.
Both Aberdeen and Pierre, S.D., are looking at highs of 100 degrees on Saturday, with upper 90s to near 100 ubiquitous across the Plains, the lower Mississippi Valley and most of the South ahead of the southward-sagging cold front. The front probably won’t make any additional southward progress before the next pulse of arriving warmth scours out any extant temperature air. Instead, the sauna-like steam bath is about to reign once again.
The heat is tied to an upper-level ridge, or a crest in the jet stream. This roadblock shunts fierce high-altitude winds and storminess to the north over Canada and the Great Lakes, with sunshine and high pressure building in to the south. High pressure areas bring sinking air, which warms up and dries out. The result? The heat dome bakes the landscape beneath it.