July 27, 2021

A Nationwide Heat Wave Leads To A Severe Weather Risk On Wednesday


Hey, hey—it's a story about heat that's not just about the west! Aren't we special? A large ridge of high pressure building over the central United States will intensify the heat most of us are feeling this week. Highs will soar into the 100s in the northern Plains while unbearably humid conditions spread over the central and the southern states. The edge of the ridge could foster a risk for severe thunderstorms in parts of the Midwest and Mid-Atlantic on Wednesday.

The pattern over the U.S. this week is the classic, putrid mess that we have to go through at least once every summer. 

Source: Tropical Tidbits

A big ridge of high pressure parked over the center of the country will send temperatures soaring, which is no small thing given how high humidity levels are right now. Some communities could see a dew point around 80°F, which is near the upper end of how muggy it can feel without actually diving into a boiling pot of spaghetti.

If you're looking for relief, the only spots to find it outside of the mountains will be the Northeast and parts of the Great Lakes, where temperatures will gradually cool off toward this weekend as an upper-level trough settles into the region. 

For everyone else, though, it's going to feel just awful.

Source: CDC

Heat advisories and excessive heat warnings festoon the National Weather Service's alerts map like an art project, warning of temperatures and humidity levels that could quickly lead to heat-related illnesses if you're not careful.

Adults don't need to be told to stay inside and take it easy, of course, but it's really easy to underestimate how much of a toll the heat and humidity take on your body. Even a healthy, physically-fit person can fall victim to heat exhaustion or heat stroke in short order when it's this hot out. 

As with any summertime heat wave, there's a risk for severe storms along and near the outer edge of the ridge responsible for the hot temperatures.


The Storm Prediction Center highlights a risk for severe weather from the Dakotas straight down to the D.C. area, with the greatest risk for severe weather existing over the Upper Midwest.

Overlaying Wednesday's severe weather outlook with Wednesday's high temperature forecast does a great job illustrating how the threat for severe weather follows the edge of the ridge, which appears as a temperature gradient:


This kind of a heat wave is ripe for the formation of a squall line, with a risk for damaging straight-line wind gusts. A squall line that's particularly intense and lasts for a long time can be called a derecho. Don't worry whether or not it'll be a derecho. Just know that there's a risk for severe weather and plan accordingly, charging up your devices and keeping flashlights handy so you can find your way around without draining your phone battery.


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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I ran Gawker's The Vane for two years and I've contributed to Mental Floss, Forbes, Popular Science, and the Washington Post's Capital Weather Gang. I also teamed up with Outdoor Life to write a book called The Extreme Weather Survival Manual, which came out in October 2015.

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