EF2 tornado in Guthrie County, Iowa

An NWS storm survey determined that an EF-2 tornado touched south southwest of Guthrie Center and tracked northeast across Lake Panorama and dissipating shortly thereafter.

Low pressure over Kansas moved northeast during the afternoon of the 11th into the morning of the 12th. By dawn on the 12th, the low was over northeast Kansas. A cold frontal boundary extended northeast from the low into northwest Iowa. The atmosphere became unstable and was strongly sheared. CAPE had increased to around 3000 J/kg by the late afternoon. Downdraft CAPE was in the 800 to 1200 J/kg range with available CAPE in the -10 to -30 C layer of the atmosphere around 600 J/kg. The lifted index was between -6 and -9 C. The freezing level had risen to around 14,000 feet. Deep moisture was drawn into the state on a 40 kt low level jet. Precipitable water values were in the 1.3 to 1.5 inch range. The LCL was quite low around 750 meters The atmosphere was strongly sheared with 55 to 65 kts of effective shear available. Thunderstorms formed along the cold front with initial development to the southwest of Iowa. The storms developed northeast into Iowa and became severe. There were numerous reports of high winds near 70 MPH, along with quarter to ping pong ball sized hail. Several funnel cloud reports were received as well. Flash flooding became a problem in Cass County near Atlantic. A NWS survey team found that 4 tornadoes touched down in Guthrie, Dallas and Boone Counties. One tornado formed south of Guthrie Center and tracked just over 10 miles northeastward and dissipated northeast of Lake Panorama where high end EF-1 and low EF-2 damage was found. The average path width was 240 yards with maximum wind speed of 115 MPH. A second tornado was an EF-1 tornado that formed on the west side of Lake Panorama and tracked east northeast to just south of Yale before dissipating. The third tornado was just north of Dallas Center in Dallas County and ended about 5 miles northwest of Granger just before reaching HWY 141. It was an EF-0 tornado with winds of 85 MPH. The fourth tornado was also an EF-0 occurring in Boone County where it touched down to the southeast of Luther.