Fox News Weather Center

Derecho Risk From Chicago to Columbus

Ingredients are coming together across parts of the Midwest and Ohio Valley that could potentially trigger a derecho on Wednesday into Wednesday night.

While it isn't exactly a certainty whether or not a derecho will form, some of the cities and towns most at risk include Chicago, Ill.; Columbus, Ohio; Fort Wayne, Ind.; Aurora, Ill.; Dayton, Ohio and Davenport, Iowa, to name a few.

Strictly speaking, a derecho is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. These showers and thunderstorms produce wind damage over a large swath of land.

While wind gusts form, derechos can sometimes reach wind speeds over 80 or even 100 mph, the vast majority of observed wind reports are usually between 60 and 70 mph.

Wind speeds of 60 or 70 mph can uproot trees, snap off large branches and bring down utility poles and wires. Due to the widespread nature of these wind gusts, power outages can also be far-reaching.

Additionally, these kinds of wind speeds can cause minor damage to structures, including roofs on houses, and they can lift any unsecured objects left outside.

Even if a derecho does not evolve on Wednesday and Wednesday night, powerful thunderstorms will still be quite numerous across much of Illinois, Indiana and Ohio.

Thunderstorms will begin near Davenport, Iowa and northern Illinois. The thunderstorms that develop here will have the ability to take on some rotation, and a few tornadoes are possible, especially in and around Davenport, Rockford, Ill.; Sterling Ill.; Ottawa, Ill. and Chicago.

The thunderstorms will then begin to congeal into a bowing, or backward 'C' shaped line as they reach northern Indiana or Lake Michigan. How much of a bowing shape the thunderstorms can take on will play a role in determining how much wind the storms can produce, and ultimately, whether or not a "derecho" fully evolves.

The worst of the storms will likely be in the afternoon across western Iowa into northern Illinois and Indiana. In places such as Ohio, the most dangerous storms may hold out until the evening hours or even after dark. Still, there could still be a stray thunderstorm around even before the main line arrives.

If you will be out and about on Wednesday night or have any plans Wednesday evening or night, you will need to pay special attention to the weather as this could be a particularly dangerous situation.

Once thunderstorms develop, they will strengthen quickly, and dangerous conditions could follow soon after.

While the situation this week does not favor a broad area of new flooding problems, storms at the local level can cause incidents of flash and urban flooding. Additional rainfall onto area streams and rivers can lead to new rises on the waterways.

Current technology has advanced enough over recent years to provide ample alert of the potential for severe weather and the approach of localized severe storms. Be sure to understand the difference between a watch and a warning. A watch means that an area is being monitored for dangerous weather. A warning means that dangerous weather is imminent. When a warning is issued, there may be too little time to travel across town or across a county to escape the storm. The time to have a plan of action and move to the general vicinity of a storm shelter or safe area is when a watch is issued.

Keep in mind that lightning is one of Mother Nature's most dangerous killers. If you can hear thunder, you are close enough to the storm to be struck by lightning, even if the sun is still shining.