“PDS severe thunderstorm watches are rare, and reserved for only the strongest thunderstorm events,” CNN meteorologist Brandon Miller said. “Wind gusts are expected to reach up 100 mph with the line of thunderstorms as rolls across northern Illinois and southern Wisconsin.”
A wind gust of a 106 mph in Marshall, Iowa, has already been reported as this storm passed through.
A derecho (pronounced similar to “deh-REY-cho”) is a widespread, long-lived wind storm associated with a band of rapidly moving showers or thunderstorms.
This storm complex is within the same area that is also under a moderate risk (level 4 of 5) for severe storms. The SPC upgraded this risk level Monday afternoon because of the formation of the derecho. The risk area includes over 13 million people.
In addition to wind damage, large hail — one and a half inches in diameter — is possible and a couple tornadoes possible.