For the second consecutive Tuesday evening, a relatively small percentage of the 24-county South Central Nebraska area was ravaged by significant severe thunderstorms that caused countless instances of damage including (but not limited to): broken windows/damaged siding, flipped irrigation pivots, destroyed crops by the thousands of acres, and more isolated occurrences of outright-demolished outbuildings/grain bins along with relatively minor structural damage to a few homes. Unlike the event a week prior on the 7th that featured a few separate swaths of severe weather, this one that played out mainly between 9:30 p.m. CDT on the 14th and 3:30 a.m. CDT on the 15th was highlighted by just one narrow, west-southwest to east-northeast oriented swath of multiple training supercells. In fact, some locations (Hastings and York to name a few) actually endured three to four SEPARATE severe storms over a span of 2-4 hours! With only limited exception, the vast majority of storm reports emanated from a 10-20 mile wide stripe centered roughly along a line from Elwood-Kearney-Doniphan-York. Within this zone there were numerous reports of large hail (many golf ball to tennis ball size) and damaging winds mainly in the 60-75 MPH range (but isolated pockets of 90-100+ MPH...especially east Highway 14). In addition, an EF-2 tornado was confirmed in southwest York County. Also of note was that some very unlucky locales experienced nearly a repeat performance of what just unfolded seven evenings prior...struck by another round of large hail/damaging winds only days after starting to recover from the first event on the 7th. Although this overlapping damage was somewhat evident over northeastern Adams County, it was particularly visible within the southwestern quadrant of York County, where many fields were mostly stripped bare for miles around...creating a visually striking/eerie contrast to what is typically a sea of green under the mid-June sun.
Taking a deeper dive into storm reports and starting with the EF-2 tornado, storm surveys concluded that it tracked just over seven miles through southwestern York County shortly after midnight CDT, developing west-southwest of Lushton and lifting west of McCool Junction. Along the way, several farmsteads sustained damage (including a garage torn from a home and a wood frame outbuilding completely demolished) and two people sustained minor injuries. Interestingly, an unofficial mesonet station in or very near the tornado path actually measured a 90 MPH gust a few miles east-northeast of Lushton. Turning to the many known (and countless unknown) occurrences of large hail/damaging straight line winds within the primary convective swath, a few of the more noteworthy wind damage/speed reports included: estimated 105 MPH winds in the Waco area that toppled a 60 ft. concrete silo; estimated 95 MPH winds through parts of northeastern Clay County that crumpled a grain bin near Saronville; widespread tree and sporadic structural damage in McCool Junction; separate measured wind gusts of 75 and 65 MPH at Hastings airport (from different storms 45 minutes apart); an unofficial mesonet gust of 79 MPH near Norman. Meanwhile, a few of the most notable hail reports featured: stones up to tennis ball size in York and Trumbull; hail up to 2.25 diameter at the NWS Hastings office that significantly dented the vehicles of on-duty meteorologists working this event; various reports of ping pong ball to golf ball size hail in or near Waco, Riverdale, Lushton, Bertrand, Kearney and seven miles south of Elwood. Rainfall-wise, despite the passage of several storms over the same areas, progressive storm motions mitigated the threat of significant flooding by limiting most totals to no more than 1-2 (highest NeRAIN amount of 2.67 on the east side of York). Although the vast majority of hail/wind reports were tied to the aforementioned west-east corridor bisecting the heart of the area, two severe storms occurred well outside of this zone...one to the south/one to the north. The southern one was a discrete supercell that lumbered through parts of Webster/Nuckolls/Thayer counties but yielded only one report of quarter size hail in Nelson. Meanwhile, the northern-most severe storm was the left-split of a supercell that first developed southwest of Kearney, dropping 1.5-2 diameter hail in the Pleasanton and Loup City areas before weakening.
Examining event evolution/meteorological background, the first weak convection of the evening within South Central Nebraska bubbled up in the Hastings area shortly before sunset, forming slightly north of a well-defined, southwest-northeast oriented quasi-stationary front stretched from west-central KS through southeast NE (storms that developed directly along this front earlier in the evening remained just southeast of the local area). Between 9-10 p.m. CDT two supercells quickly evolved out of the initial weak activity, one that pounded York with its first round of large hail and drilled the eastern part of the county with significant wind damage, and the other the aforementioned southern supercell that developed over Webster County. Between 10-11 p.m. CDT, these first severe storms either departed the local area into eastern Nebraska (the northern one) or weakened/dissipated (the southern one). However, not far to the west the primary supercell train was just getting warmed up as several severe storms rapidly blossomed along the Highway 6/Interstate 80 corridors within the western half of South Central Nebraska. This slightly-elevated activity developed in response to intensifying nocturnal convergence into a sharpening frontal zone very evident in the 850-700 millibar layer. Given that this low-mid level front was aligned nearly parallel to strong west-southwesterly upper level winds (attendant to a large scale trough centered over the Northern Rockies) and that the mesoscale environment featured a potent combination of very strong deep layer shear (50-70 knots) and decent most-unstable CAPE (1000-2000 J/kg), the stage was set for a somewhat rare episode of several supercells training along the same corridor in close succession. In fact, between 11 p.m. and 2 a.m. CDT, at least 3-5 severe-warned storms marched in tandem along this path, each core spaced out roughly 25 miles from the next. During this three-hour span, places such as Hastings and York endured three separate severe storms (bringing York up to FOUR direct hits...including the initial supercell of the night). While most of these cells remained just elevated enough to preclude a tornado threat, the first storm in the supercell train managed to spawn the EF-2 in southwestern York County...apparently tapping into JUST enough lower-level moisture/instability in the vicinity of the nearby surface front to become tornadic. Finally, between 2:00-3:30 a.m. CDT, the last two training supercells of the night passed through Hamilton, Polk and northern York counties before departing the local area, bringing an end to this unique and (in places) destructive event.