AccuWeather meteorologists are monitoring the potential for a high-powered, long-tracking and fast-moving batch of thunderstorms, known as a derecho, to develop later this week across parts of the central United States.
In simple terms, a derecho behaves like an inland hurricane with a large batch of damaging winds and heavy rainfall that can at times lead to significant flooding.
The National Weather Service has developed criteria to distinguish derechos from other, less intense and shorter-distance thunderstorm complexes. In order for a derecho to be declared, usually via a post-storm analysis, the storms must have traveled 400 miles or more with a width of at least 60 miles. The storms also must have produced damage nearly continuously along that path.
However, there will still be a significant risk to lives and property from a complex of severe thunderstorms this week–whether a derecho is officially declared or not
“Complexes of thunderstorms will erupt near and north of the rim of tremendous heat, which is anchored over Texas and the southern Plains this week,” said AccuWeather Senior Meteorologist Dan Pydynowski. “One day and night in particular – Thursday – may represent a higher risk for a derecho.”
The first storms are likely to erupt Thursday afternoon, and there are two zones where a derecho may develop, AccuWeather forecasters say.
“Data suggests that much of Nebraska, northern Kansas, northwestern Missouri and southwestern Iowa will be one area at greatest risk for severe thunderstorms during Thursday afternoon and evening,” said Pydynowski.
From this zone, should an intense complex of storms evolve, it may continue to roll through the late-night hours Thursday and then across the middle portion of the Mississippi Valley and then perhaps into portions of the Ohio or Tennessee valleys Friday.
“The exact initial eruption of thunderstorms on Thursday and their intensity will determine how long they may survive and which areas may be hit or missed by the complex hundreds of miles away a day later,” AccuWeather Senior Meteorologist Brett Anderson said. It is possible a long-lived complex such as a derecho could reach as far as parts of the southern and central Appalachians.
At roughly the same time Thursday afternoon, thunderstorms will erupt and may try to organize into one or more complexes in portions of Illinois, Indiana, western Ohio and Kentucky.
These storms may then roll southeastward with the core of the heat to the southwest and more temperate air to the northeast through Thursday night and into Friday.
Because there are multiple areas where thunderstorms could merge into dangerous and far-reaching complexes, it is possible that some places could be hit by two rounds of dangerous thunderstorms in 12 hours.
Just as all thunderstorms are not created equal, the same is true for derechos.
On August 10, 2020, an intense derecho produced a swath of high winds and leveled crops from eastern Nebraska to parts of Michigan and northern and central Indiana. The damage swath extended for nearly 800 miles with a peak wind gust of 126 mph recorded in Atkins, Iowa.
That derecho resulted in at least four fatalities and more than $11 billion in damages across the Midwest.
On June 29, 2012, one of the most powerful derechos in recent memory caused substantial damage to the Washington, D.C., area. The storm produced significant wind damage along an 800-mile path from Iowa to the Delmarva Peninsula.
Into Wednesday night, individual thunderstorms, as well as clusters of storms, will stretch from the eastern parts of Montana, Wyoming and Colorado, as well as much of the Dakotas and Nebraska to portions of Minnesota, Iowa and Wisconsin.
Into Tuesday night, the risk of heavy to locally severe thunderstorms will target the heavily populated and highly traveled mid-Atlantic region. This is in the wake of powerful storms that brought high winds and torrential downpours to the region Monday.
Severe thunderstorms are in store for parts of the lower Mississippi Valley and the central Gulf Coast Wednesday.
In most cases, the greatest threats from these storms will be localized damaging wind gusts and flash flooding. Some of the storms, especially those over the Plains and Midwest, may also produce large hail. Any severe thunderstorm, when the atmospheric conditions are right, may generate a brief tornado.
By this weekend, the heat dome over the South Central states will break down and the risk of a derecho should lower. However, as weather systems continue to move along from west to east across the nation, there can still be episodes of thunderstorms, including some severe weather, in the central region.
Produced in association with AccuWeather
Edited by Joseph Donald Gunderson and Alberto Arellano
