Thunderstorms have been riding along the edge of a heat dome in the middle of the country for weeks, and Labor Day weekend is expected to bring more of the same. High temperatures will bake the Central United States, and the chance for severe storms will shift from the Great Lakes and Mid-Atlantic into the Southeast, forecasters say.
Extreme heat warnings and heat advisories are in effect from Kansas and Illinois to Alabama and the Carolinas into the long weekend. Forecasters have warned people across the Southeast to brace for potential strong thunderstorms, much like those that dotted the northern part of the country this week.
A heat dome is an area of high pressure in the atmosphere that traps warm air at the surface, and one has been present across much of the middle of the United States for weeks. It has continuously driven up temperatures across the Southern Plains — in Kansas, Oklahoma and Texas — and also in Missouri, Arkansas and Louisiana .
“It has been nonstop heat for at least a month now,” said Phil Ware, a meteorologist with the National Weather Service in Norman, Okla.
Oklahoma City recorded its fourth-hottest August on record, with data going back to 1891.
“That ridge has been keeping us hot and dry and blocking any weather systems that would bring rain or cooler air,” Mr. Ware said. “It’s part of why we’re seeing flooding and thunderstorms to the north.”
The storms have been rumbling through the Midwest and into the Mid-Atlantic for weeks. They have been traveling along the periphery of the high-pressure ridge, mainly along the north and northeast edges, which is why some meteorologists refer to them as ridge riders.
This setup fueled the nonstop soaking that Indiana and Ohio received last month. The cluster of long-lasting, powerful storms, known as a derecho, kicked up damaging winds as it moved from Iowa and Illinois into northern Indiana in mid-August. Residents of Gary, Ind., were without power for days.
On Thursday, storms traveled from Michigan southeast into Maryland and Virginia, leaving wind and hail damage in their wake. A tornado touched down on the east side of Detroit, according to a preliminary report. The Weather Service said it was waiting on a damage survey to confirm details.
The day before, storms tore through Toronto, causing significant flooding and damaging Rogers Stadium, a temporary outdoor venue that hosts major concert tours. Storms also generated weak tornadoes in upstate New York.
The Weekend Forecast
On Friday, the threat for severe storms spanned Michigan to North Carolina. It is expected to gradually shift south over the weekend, centering on the Carolinas and potentially bringing heavy rain and damaging winds.
“These storms will be on the eastern side of the ridge,” said Jared Guyer, a lead forecaster with the Storm Prediction Center, an arm of the Weather Service.
On the Labor Day holiday on Monday, the storms are expected to push even farther south over South Carolina, Georgia and Florida.
Outside of the South, cooler air is expected to pour into the Midwest and Northeast. Sunny skies with temperatures in the 70s are expected in New York City on Monday.
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