EF1 tornado in Dawson County, Nebraska

A tornado developed within a line of thunderstorms northwest of Johnson Lake in far southern Dawson county just before 11:00 PM on Friday, May 5th. The tornado appeared to begin a couple miles northwest of the toppled three irrigation pivots before hitting the Lakeview Acres area on the northwest side of the lake. At least two large storage sheds were totally destroyed in that area. There were several instances of damage in the area, such as trees, smaller buildings, windows and some roof damage,

including two 2x4 stud driven into the roof of one home. The tornado traversed east across the lake and did significant damage to several homes on the east side of the lake right along the Gosper county line. Along the shore line, at least three homes in a row had all or part of a covered porch blown apart, and one home had a large section of its roof torn off. Another flat roof cabin had its entire roof torn off. A few power poles were snapped. Tree damage was common in this general area. The tornado moved east and upset an irrigation pivot and peeled back some metal roofing from a large building just east of the lake. The tornado likely dissipated east of County Road 428. The

maximum wind speed was estimated to be 95 MPH based upon the residential roof damage and the storage building being destroyed. The path was just under 5 miles long and the width was estimated to be 80 yards.

Large hail, damaging wind gusts, and an isolated tornado occurred over portions of south central Nebraska, mainly west of Highway 281, during the afternoon through late evening hours. Initial development occurred roughly along the NE/KS state line between 1600-1700CDT, and was mainly in the form of supercells. By around 2200CDT, nearly a half-dozen supercells affected portions of south central Nebraska roughly along and south of Interstate 80 (I-80) and west of Highway 281 and produced scattered instances of large to very large hail. The largest hail reported was tennis ball in Franklin County, which was associated with one of the first supercells to form in the late afternoon. After the initial round of supercells, which weakened mostly below severe limits by 2230CDT, a squall line of thunderstorms moved into far western portions of the CWA between 2230-2300CDT. The primary severe threat with this activity was damaging wind gusts of 60-65MPH. However, embedded within the squall line was a brief EF-1 tornado that impacted the Johnson Lake area around 2300. A bow echo developed within the squall line between 2300-2400CDT over Dawson County then raced northeast and affected areas north of the Platte River over the next 60-90 minutes. This activity weakened as it exited NE portions of the CWA during the early morning hours of May 6th.

While there were no significant synoptic scale fronts or low pressure systems in the area of this event, the first round of scattered supercells developed along a remnant outflow boundary that was stalled near the NE/KS state line. The second round was a result of thunderstorms that developed over the High Plains which was then supported by an increasing low level jet as activity shifted east overnight. Through the entire event, there was moderately strong instability (2000-3000 J/kg of CAPE), strong deep layer shear around 40-45kt, and steep mid level lapse rates of 7-8C/km. 0-3km shear was also strong during this event, around 30kt, which supported the bow echo development across northern portions of the CWA during the evening hours.