Tornadoes and Hail in Illinois, May 18, 2000

A frontal boundary meandering about Southern Iowa and Central Illinois lifted into Central Iowa and North Central Illinois by afternoon. A nearly stacked low center over the Mid Missouri River Valley underwent filling as it shifted eastward across Southern Iowa and Central Illinois. Much of Northern Illinois along and north of Interstate 88 was thrusted into the warm sector where temperatures climbed into the upper 70s to lower 80s. Meanwhile, areas north of the boundary were quite cool with a brisk northeast surface wind and plenty of cloud cover keeping temperatures down in the 60s. 12z soundings from KILX and KDVN indicated very steep lapse rates with Cape values of 2000-3000 J-kg. Thunderstorms quickly erupted along the boundary from Central Iowa through Northeast Iowa into Northern Illinois by late morning, and continued through the afternoon. The storms produced large hail, heavy rain, damaging winds and several tornadoes over portions of Northwest Illinois. Thunderstorm interaction with the frontal boundary was believed to be the culprit for spawning 6 weak and short lived tornadoes across Henry and Bureau Counties. The only damage occurring with the tornadoes was in Manlius and Neponset where large trees and signs were blown down. High winds, associated with a possible gustnado, blew down the back wall and knocked out several windows of an abandoned grocery store in Cambridge. The glass and bricks were hurled to the ground, causing damage to a truck parked on one side of the building. The high winds also downed several trees and power lines. Power was knocked out to Cambridge and surrounding areas for almost 4 hours.