EF0 tornado in Winnebago County, Iowa

A cone tornado was on the ground briefly east of Rake.

Warm and very humid air moved north into Iowa during the day on the 17th. Surface temperatures warmed into the mid 80s to low 90s, with dew point temperatures in the mid 70s to around 80 by mid afternoon. A weak cold front was approaching the state at the same time that a negatively tilted shortwave lifted northeast across the upper Midwest. The atmosphere became very unstable with lifted indices falling to around -9 C. CAPE rose to between 3000 and 4500 J/kg by late afternoon. Downdraft CAPE was around 1500 J/kg with available CAPE in the -10 to -30 C layer of the atmosphere between 800 and 1100 J/kg. With the humid airmass, precipitable water values were between 1.8 and 2 inches, resulting in a relatively low LCL level of 750 to 1000 meters. The freezing level was relatively high, around 14,500 feet. The shear was not all that strong, ranging from around 35 kts over northern Iowa to 20 over the southwest. Thunderstorms fired up initially during the mid to late afternoon hours. The storms consolidated into a solid line during the evening and advanced east-southeast across the state. During the early stages of the development, the thunderstorms produced several tornadoes. One touched down briefly near Lakota in Kossuth County along U.S. Highway 169. A second tornado tracked from southwest of Lakota to north of the city. A third tornado was on the ground briefly east of Rake in Winnebago County. The storms then transitioned into more of a wind and hail event. Due to the warm conditions aloft, most of the hail was only around in inch or so in diameter. Golf ball size hail fell in the Buffalo Center area of Winnebago County. The largest hail was a report of baseball size hail west of Ledyard in Kossuth County. Winds increased as the evening went on and the system accelerated. Tree damage was reported in several locations with winds gusting in the 60 to 70 MPH range.