Thunderstorm Wind — Polk, Nebraska

2024-06-07 · near Osceola, Polk, Nebraska

Event narrative

NWS COOP Observer estimated 60 MPH winds that downed some tree limbs in town.

Wider weather episode

Between 5-11 p.m. CDT on this Friday afternoon-evening, four intense and at least semi-discrete supercell storms charged east-southeast through parts of South Central Nebraska, each yielding concentrated swaths of large hail and/or damaging winds...destroying young crops and causing varying degrees of damage along the way. The northern-most supercell primarily impacted parts of Valley, Greeley, Nance and Merrick counties. Meanwhile, the other three supercells tracked in fairly close proximity to one another, cumulatively raking through primarily parts of the following counties: Sherman, Dawson, Buffalo, Hall, Phelps, Kearney, Adams, Franklin and Webster. Primarily within the aforementioned counties, numerous sensors (mostly unofficial personal stations) clocked gusts of 60-70 MPH, but ground-truth reports/photos of damage to irrigation pivots, power poles, trees and grain bins/outbuildings clearly revealed embedded swaths of fiercer speeds at least 70-85 MPH. A few of the most notable corridors of wind damage included: 1) an expansive swath several miles wide extending from eastern Valley County across Greeley County into Nance/Merrick counties (countless irrigation pivots flipped through this area)...2) a roughly 10-mile-long stripe of estimated 85 MPH winds that tore through eastern Phelps County (Funk vicinity), flipping numerous irrigation pivots, snapping several power poles and destroying an aged barn. Turning to hail, the largest reported stones were mainly in the golf ball to 2-inch diameter range, including in or near the following communities: Minden, Heartwell, Bladen and Litchfield. However, the largest reported baseball size hail pummeled the Norman area of eastern Kearney County. Comparatively smaller, but still severe-criteria hail of quarter to ping pong ball size hail fell in or near places such as: Gibbon, Greeley, Ravenna, Shelton, Wood River, Miller and Franklin. Although of lesser consequence than the wind damage/large hail that occurred, a large scale/composite outflow boundary that pushed out ahead of the western three supercells prompted expanses of blowing dust, with a storm chaser reporting near-zero visibility along Highway 136 near Inavale. As for the Tri Cities, all three avoided the main cores of the four supercells (including large hail), but various sensors in Kearney (including Kearney Regional Airport) clocked gusts up to around 60 MPH...with some tree damage reported in town.

Breaking down the timing and evolution of this event, this was a fairly well-anticipated severe weather setup as SPC assigned a Slight Risk (level 2 of 5) to the entire 24-county South Central Nebraska area on its Day 2 Convective Outlook, followed by an upgrade to Enhanced Risk (level 3) for parts of the local domain on the morning of the 7th (Day 1). In the big picture of the mid-upper levels, there were no strong/distinct disturbances in play, but broad west-northwesterly flow strengthened in response to a subtle/low amplitude wave drifting out of Wyoming into Nebraska during the afternoon-evening. At the surface, low pressure gradually intensified over northwestern Nebraska over the course of the day, positioning the local area within a broad warm sector featuring steady south-southeasterly breezes and dewpoints rising into the low-mid 60s F. During the mid-afternoon, the initial severe storms/supercells blossomed 50-100+ miles northwest of the local area over the heart of the Sandhills, but this intense convection soon started marching toward South Central Nebraska...where it would encounter a potent mesoscale environment featuring mixed-layer CAPE of 1500-2500 J/kg and seasonably-strong effective deep-layer wind shear of 50-60 knots. The first/northern supercell to invade South Central Nebraska arrived into northern Valley County shortly after 5 p.m. CDT...then tracked east-southeast through northern local counties for the next three hours before weakening somewhat over Polk County and exiting into eastern Nebraska around 8 p.m. CDT. Meanwhile, back to the west and southwest, the second South Central Nebraska supercell of the evening entered southwestern Sherman/northeastern Buffalo counties between 6:30-7:30 p.m. CDT. Shortly thereafter, between 7-8 p.m. CDT, two additional, trailing supercells followed quickly on its heels, with one core entering the local area into northwestern/central Buffalo County and the western-most supercell dropping into eastern Dawson County. As a result, by 8 p.m. CDT, three semi-discrete supercells were aligned in west-east fashion along the Interstate 80 corridor from eastern Dawson to western Hall counties...their central cores separated by roughly 20 miles. Between 8-10 p.m. CDT, the leading/eastern storm weakened before reaching the Hastings area, while the western two cells remained severe while stomping southeastward through parts of primarily Phelps, Kearney, Franklin and Webster counties. Finally, between 10-11 p.m. CDT, these pair of cells gradually weakened and congealed into a more linear complex while exiting the far south/southeast reaches of the local area into northern Kansas/southeast Nebraska.

View location on OpenStreetMap → (41.1800, -97.5500)

Source: NOAA Storm Events Database, event_id 1201836. Narrative written by the NWS forecast office that issued the report.