Over the weekend, the expanding pulse of a warm dome of high pressure parked over the southern tier is sweeping across most of the central Lower 48 with record and near-record strength at its center. It's just getting started.
“A major heat wave is expected across much of the Midwest and extends across the central and southern Plains until about [next] Thursday,” wrote the Weather Prediction Center in Friday's debate.
Beneath the heat dome, dozens of daily highs are at risk, and some monthly or all-time highs may also fall, including in places that have already piled up heat records this summer.
Extreme heat to sweep across central US
Thursday was the last day of extreme heat in the Northwest before a cold front moved through. Record temperatures have been common since Sunday in the region, including a monthly record high of 108 in Portland. Many other daily records were set in Texas and surrounding areas.
Temperatures around 15 to 20 degrees above normal prevail over the northern and central high plains on Friday. parts of montana, the Dakotas, Wyoming, then south to the central and southern plains reach or exceed 100.
Rapid City in southwest South Dakota is forecast to reach 103 on Friday, which would threaten a record for the date. Places just east of it can get as high as 107 or so.
Persistent unseasonable heat is likely to anchor the Central Plains and Midwest, and the South and Southeast. Extended temperatures above 100 degrees are possible this weekend from Nebraska and Missouri south to the Gulf Coast.
Most locations in Texas will records threatened Friday. Dallas is forecast to reach 110, which would be a new record for the date. Records are also in jeopardy over the weekend, with highs of 108 to 110 by Monday. Austin is projected to reach 106, while Houston is nearing 100.
On Saturday, about 4 dozen long-term sites could see record highs. Oklahoma City is forecast to hit 106 on Saturday, with Wichita hitting 107. To the south, New Orleans threatens records again just Saturday, with a forecast high of 100 there.
Once the extreme heat sets in, it won't ease up much or at all during the week. Temperatures near and above 100 continue into Thursday or Friday for many of them the same locations.
Record highs should tend to be concentrated in the Midwest and South by midweek. Des Moines could be near a record high on Tuesday, with a forecast of 101. On Wednesday, Minneapolis is expected to approach 100 as well.
Incredibly, even on average over a week, weather models suggest temperatures could be 15 degrees or more above average – punishing, unbearable heat.
Great heat, in a widespread way
After a brief break in sub-100 degree temperatures over the past few days, a high of 108 on Thursday set a record for the date in Dallas. Waco also reached 108, a record there.
An extreme heat warning until Sunday could be extended due to the forecast. Some good news for the region is that humidity may remain lower than usual in mid-summer. This means that heat index values are close to or right on top of temperature in most places.
Salina, in northeast Kansas, could see at least a week of highs in the 100s or above in most weather models starting Saturday and continuing through at least Friday. If that happens, it will be the longest streak since 2012 there. The Weather Service is predicting 108 there on both Saturday and Sunday.
“Models produce warmest low-level temperatures in 20-year weekend reanalysis”. the Weather Service wrote in Omaha.
In the area near and north of northern Kansas in Nebraska, Iowa and Missouri, moisture levels may also increase. This can be attributed in part to huge crops, mainly corn, adding moisture to the air through “corn sweat.” An oscillating frontal band north of there is also helping to gather moisture.
In those areas, heat indices could reach 115 or even 120 under the right conditions, almost every day in some spots this weekend into next week.
By mid to late next week, widespread temperatures around 100 or higher are possible from the same areas that will see it over the next few days up the East Coast. A prolonged period of extreme heat may eventually take place from the Mid-Atlantic to the Southeast.
The summer of 2023 was marked by extreme heat that bounced from place to place, focusing its wrath on places like the Desert Southwest and the Gulf Coast.
This heat dome expansion may be the broadest of the summer. Early next work week, most of the Lower 48 is forecast to see well above normal temperatures, with the West being the lone exception.
Above normal temperatures look set to stick around for the rest of the month in most places.
At a longer range, around 10 to 14 days or so, the heat dome may eventually compress a bit to the south. That may not mean much or any relief for those hardest hit by the heat like Texas.
The persistence of high temperatures is a hallmark of climate change. Incidents of unrelenting heat, often caused by slow or delayed weather conditions, have been numerous in recent years around the world. A strengthening El Niño, characterized by warm water in the equatorial Pacific Ocean, also adds fuel in 2023.
