Hail — Harlan, Nebraska

2023-06-29 · near Stamford, Harlan, Nebraska

Event narrative

A cluster of thunderstorms sliding east just north of the Nebraska-Kansas state line produced widespread severe weather across central and southern portions of Harlan County. Hail generally up to the size of golf balls was reported across this area, though isolated larger hail also likely fell. Wind gusts were estimated to be anywhere from 60 to 70 MPH, resulting in numerous reports of tree damage, including whole trees snapped and larger limbs downed. A farm machine shed was destroyed between Stamford and Orleans. The wind-driven large hail resulted in widespread damage to crops, siding, windows, and vehicles.

Wider weather episode

Although it only impacted a small portion of South Central Nebraska, this very early Thursday morning was a destructive one within a few far southern counties as one of the fiercest (if not the fiercest) supercell thunderstorm of the local 2023 convective season raged across primarily the southern halves of Furnas/Harlan counties into southwestern Franklin County...laying down a concentrated swath of large hail/damaging winds before mercifully weakening as it slid farther east into southeastern Franklin and southern Webster/Nuckolls counties. This storm/supercell cluster had actually been trucking along for quite some time before invading the local area (see event evolution details below). Per numerous storm reports (and confirmed by post-event satellite imagery), the primary west-east swath of damage was only 5-10 miles across...centered almost directly along a line from Wilsonville-Beaver City-Stamford-Alma-Naponee. Within this corridor, the combination of large hail (some stones to at least baseball size) driven by wind gusts of at least 60-70 MPH prompted countless instances of damage such as: broken windows/damaged siding at homes/businesses, flipped irrigation pivots, crops destroyed by the thousands of acres, and more isolated occurrences of significantly damaged or demolished outbuildings. This was a fairly quick-hitting event within South Central Nebraska, with the vast majority of severe weather in the unfolding over 90 minutes between 3:00-4:30 a.m. CDT. Taking a deeper dive into storm reports and the various documented (and countless undocumented) occurrences of large hail/damaging winds within the primary convective swath, a few of the more noteworthy accounts that garnered local media coverage included: a nasty combination of wind-driven hail (widespread ping pong ball up to isolated baseball size stones and 60-80 MPH winds) that shredded crops and shattered many windows/significantly damaged siding in and near Wilsonville, Beaver City, Stamford and Orleans...including at business such as the Wilsonville Post Office; estimated 80 MPH winds in southern Harlan County that topped several trees/large branches in Alma and destroyed a farm machine shed between Stamford and Orleans. Although the vast majority of severe weather reports occurred with the primary supercell along the aforementioned narrow swath, there were a few outlier occurrences including: estimated 60-70 MPH winds near Cambridge (along the far northern fringes of the main supercell) and ping pong ball size hail in Beaver City from a rogue, isolated storm that briefly flared up a few hours prior to the main event.

Breaking down event evolution/timing, and starting from a forecast perspective, this was not an overly-obvious setup for such a significant (albeit rather localized) severe storm event within the local area. Although some necessary ingredients were certainly present, short term/higher-resolution computer models (CAMs) varied considerably regarding how evening High Plains convection would evolve, and to what degree it would impact locales farther east (including South Central Nebraska). The 01 UTC (8 p.m. CDT) Day 1 Convective Outlook from SPC (valid through the early morning of the 29th) highlighted only a Marginal Risk (level 1 of 5) for South Central Nebraska, but also acknowledged very substantial uncertainty. In the mid-upper levels, although lacking any noteworthy, small-scale disturbances, broad and seasonably-strong west-southwesterly flow was in place over the Central Plains...downstream from a large scale, positively-tilted trough centered from the Northern Rockies to the Great Basin. At the surface, South Central Nebraska resided north of a quasi-stationary front stretched across Kansas from southwest-to-northeast, with resultant east-northeasterly breezes to the north of this boundary enhancing High Plains upslope flow. Turning to storm-scale details, the supercell that eventually roared into Furnas County actually initiated/became severe roughly 240 miles off to the west-northwest during the late afternoon of the 28th...in extreme southeast Wyoming. During the evening, the intense storm slowly lumbered southeastward through the far southwestern Nebraska Panhandle into northeast Colorado. By around midnight CDT, this convection had morphed into a powerful supercell cluster/small complex as it entered far southwestern Nebraska and started tracking more due-east...riding along the northern fringes of a tight mid-level temperature gradient (generally hugging the 12C line at 700 millibars). Out ahead of this dominant supercell, increasing low-mid level warm air advection prompted the brief flare-up of a lone strong/marginally-severe storm over Furnas/Harlan counties between 12:30-1:30 a.m. CDT (which produced ping pong ball size hail). However, this was just a small taste of what was to come a few hours later, as the notable supercell cluster reached Furnas/Harlan counties between 3-4 a.m. CDT. During the ensuing hour, this storm complex gradually weakened within Franklin/Webster counties as additional strong storms flared up out ahead of it primarily over Nuckolls/Thayer/Fillmore counties. Between 5-6 a.m. CDT the severe weather threat finally ended within South Central Nebraska for the night, as the main core of the initial supercell cluster slipped slightly south of the state line into northern Kansas, while the more widespread convection to its north remained sub-severe while gradually exiting eastward into eastern Nebraska. Although there had been considerable uncertainty whether South Central Nebraska would even see such an intense storm during the pre-dawn hours of the 29th, once it started approaching the local area from southwest Nebraska the mesoscale environment strongly supported its eastward persistence, given a formidable combination of at least 2000-3000 most-unstable CAPE and at least 50-60 knots of deep-layer wind shear.

View location on OpenStreetMap → (40.1243, -99.6301)

Source: NOAA Storm Events Database, event_id 1109316. Narrative written by the NWS forecast office that issued the report.