PEORIA, Ill. (WMBD) — Saturday afternoon was hot and humid for one side of the viewing area, but became stormy for the other edge of the region.

The unexpected round of severe storms brought damaging winds, large hail, and flash flooding in eastern McLean County around Colfax.

Damage Reports

Hail

  • 3 miles south of Fairbury – 1.75″ (Golf Ball)
  • 3 miles west of Cropsey – 1.75″ (Golf Ball)

Wind

  • 3 miles west of Cropsey – 70 mph
  • Colfax – Significant tree damage in town with numerous tree limbs down on cars and two houses with trees through the roof
  • Chenoa – Large tree limb blowing down
  • Minonk – Power line down and two power poles leaning over

Heavy Rain

  • Radar also estimated 2-4 inches of rain in the area though there was one report of 4.75″ in Colfax. This led to flooding in the area including in the Ridgeview school building where it was reported that the basement classrooms had at least 3 inches of water on the floor
  • Colfax – 4.75″
  • Saybrook – 2.75″

How Did This Happen?

How did this happen when severe weather was not in the forecast?

On Friday night, storms were expected to develop in NE Iowa and track east-southeast across northern Illinois through Saturday morning.

While there was a chance these storms would impact areas along I-74, it was more likely for these storms to impact locations along I-80, which they did.

The problems begin late Saturday morning as these storms continue to back build across Livingston and La Salle Counties, using the outflow boundary from the overnight storms (now in Indiana) as the lifting mechanism for new development.

The forecast was for these storms to move out of the area by 10 am, allowing subsidence (sinking air) to move over the area behind the departing shortwave, leaving us with hot and humid conditions.

This didn’t happen, at least not east of I-39. Instead, the storms continued to bubble up behind the outflow boundary while the atmosphere was becoming increasingly unstable just to the west.

The supercell that brought the large hail, damaging winds, and even prompted the tornado warning was able to latch on the outflow boundary itself and have access to the hot, humid, and unstable air mass sitting just a few miles to the west.

This caused the storm to explode, with cloud tops reaching nearly 60,000 feet and causing the storm to produce hail and damaging winds.

Because the storm was latched on to the outflow boundary, it was able to take on a bit more rotation near the surface, which prompted the tornado warnings across McLean and Livingston Counties.

As soon as the storm moved off of the boundary, it became elevated once more and would gradually weaken. Additional storms would develop a little bit later in Woodford County as the outflow was nudged westward.

Thankfully, these storms would fire behind the outflow and over an air mass that was overworked from the severe storms earlier in the afternoon. This minimized the risk of tornadoes, but the storms were still able to produce strong winds and hail.

This event is a good example of how one thing going wrong or different than expected can set off a chain reaction of events that can lead to significant storm damage.

Eyewitness Account

This is from a farmer just outside of Colfax:

“We’ve been missing the rains since we placed the seed in the ground on May 1. So about an hour before the storm, I set out crop scouting. Most of these cells have missed us, and the projection was that this one wouldn’t be any different. I was in Elliot, five miles east of Gibson City, when I realized that it was going to build over Anchor and take an unexpected turn south towards Saybrook. This put our farmstead in the direct path. I rushed home to prepare with roughly 10 minutes to spare. During that time, my wife and I took some photos and videos. The storm seemed to pause and build around Anchor before stretching west towards Colfax and giving them 5″ of rainfall. We received 2.5”, five miles west of Gibson City. The event produced ping pong sized hail that lasted for around 20 minutes in the area I observed. After looking at crop damage, the possibility of larger hail or more intensity is evident in the surrounding fields. Localized but spotty, there is a 4-mile by 6 mile wide area that has yield affecting damage. The tops of the corn plants are shredded, and the soybean stems are cut. It has been about 5 years since an event such as this has been in our area. On the bright side, we have surpassed the prior year’s July rainfall amount.“

Tyler Young, McLean County Farmer