More destructive winds from severe thunderstorms expected to sweep across the Midwest

> AccuWeather meteorologists are monitoring the potential for a complex of 
severe thunderstorms across Iowa, Illinois and Indiana Monday afternoon 
and evening that can produce destructive winds and might develop into 
a derecho
 
>  A derecho is a high-powered, long-tracking and fast-moving batch of 
thunderstorms that can bring significant wind damage over a large area

>  Storms could impact outdoor tents and equipment at the Republican National 
Convention in Milwaukee   

> Lower temperatures and decreased humidity levels in the wake of the cold 
front will offer relief from the recent heat by midweek across much of the 
Midwest, Great Lakes and Northeast 

AccuWeather Global Weather Center – July 15, 2024

AccuWeather expert meteorologists have issued a rare “high” risk for severe thunderstorms with 80-90 mph wind gusts possible Monday afternoon and evening across eastern Iowa, parts of northern and central Illinois, and western Indiana.  

“We are concerned that these storms could develop into a damaging derecho,” said AccuWeather Chief On-Air Meteorologist Bernie Rayno. “It’s been a hot summer. This is a very steamy air mass  where storms will erupt.”  

A derecho is a thunderstorm complex with a width of at least 60 miles that travels along a path of at least 400 miles. The thunderstorm complex must have wind gusts of at least 58 mph over this path to be categorized as derecho. 

“A derecho can feel like a brief inland hurricane, although it’s a completely different meteorological setup. Sometimes the most intense clusters of storms can produce damaging wind gusts of hurricane force or even higher along a long track for hours on end,” said AccuWeather Chief Meteorologist Jon Porter. "Those powerful wind gusts, might only last in a specific place for 10-15 minutes, but can bring trees down onto power lines and even snap utility poles, leading to extended power outages.  These power outages can last days to even a week or more if there is extensive damage, especially if the damaging winds occur in a major city". 

Severe thunderstorms could impact the Republican National Convention in Milwaukee, Wisconsin Monday night.  

“Later this afternoon into this evening, severe thunderstorms could impact travel and pose a threat to tents, security barriers, stages and other outdoor equipment at the Republican National Convention in Milwaukee,” said AccuWeather Chief Meteorologist Jon Porter. “Often, outdoor stages and tents can be vulnerable to winds as low as 35 mph. It’s important that outdoor equipment is secured and appropriate safety protocols be implemented to move people outside to safe shelter in order to reduce the risk of injuries and damage should gusty storms blow through. 

"The storms in Milwaukee and Chicago will be closer to the evening commute,” said AccuWeather Senior Meteorologist Tyler Roys. “Much of Michigan and Indiana, including Detroit and Indianapolis, will have their highest risk of severe thunderstorms during the overnight hours.” 

AccuWeather expert meteorologists warn that the strongest storms could have destructive wind gusts capable of damaging homes and businesses. Wind gusts could also cause widespread damage to corn and other crops.  
 

“We’ve got a big dome of heat that plays a significant role in fueling thunderstorms, as well as supporting how long these storms can last into the evening and overnight hours,” said AccuWeather Severe Weather Expert Guy Pearson. 

There is also a “moderate” risk of severe thunderstorms across parts of northern Pennsylvania and southern upstate New York Monday. Roys says flash flooding and damaging wind gusts are the primary safety concerns.  

"Across the Northeast, thunderstorms will have plenty of heat and humidity to work with,” said Roys.  

The hot and humid air and the east-advancing cold front will push the severe thunderstorm risk farther to the south and east Tuesday. 

AccuWeather expert meteorologists are forecasting a “moderate” risk of severe thunderstorms Tuesday across much of Illinois, Indiana, and Ohio.  

"The strongest storms are expected from central Illinois to northwestern Ohio, where storms will be capable of producing flooding downpours, damaging wind gusts and hail," said Roys. 

Much of the Midwest is finally expected to get relief from the threat of severe weather by Wednesday as the cold front approaches the East Coast.  

AccuWeather expert meteorologists issued a “moderate” risk for severe thunderstorms Wednesday that will stretch from northern Maryland to southern Maine.  

"The cold front moving into a very hot and very muggy air mass in the northern Tennessee Valley, and into the Northeast and mid-Atlantic, will lead to explosive thunderstorm development," said Roys. "This time, the big cities from Washington, D.C.,   to Boston are likely to have storms during the afternoon commute or in the early evening hours, snarling travel for those driving home.” 

In the wake of the cold front, widespread lower humidity and temperatures below the historical average will arrive across much of the Midwest, Great Lakes, and interior Northeast, providing relief from well above historical average temperatures.  

As is typical in the summer, the cold front will eventually slow down and stall as it moves into the Southeast. AccuWeather expert meteorologists say this will set up a zone of potential downpours that could lead to flooding. Abnormally dry and drought conditions have been reported in this region, so outside of the areas impacted by flooding, rain will be beneficial in most areas.  

AccuWeather expert meteorologists issued an alert in June, warning of a major shift in the weather pattern that would increase the risk of derechos and thunderstorms with destructive wind gusts this summer.  
 

AccuWeather Forecast Graphics

Additional AccuWeather Resources:

Severe thunderstorm risk to stretch from Midwest to Northeast this week 

What is a Derecho?   

Major Pattern Shift Brings Threat Of Severe Thunderstorms With Widespread Wind Damage To 20 States Over The Coming Weeks