Thunderstorms over portions of western Nebraska produced several occurrences of large hail, along with strong wind gusts and locally heavy rainfall.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS CYS wrote it up.
Thunderstorms over portions of western Nebraska produced several occurrences of large hail, along with strong wind gusts and locally heavy rainfall.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Cheyenne, WY wrote its last area forecast discussion before the first event at Aug 12, 10:42 AM MST, 2 hours 51 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 1142 AM MDT Sat Aug 12 2017 .UPDATE... Issued at 1102 AM MDT Sat Aug 12 2017 Latest water vapor loop was showing shortwave energy moving through southwest Wyoming late this morning. Starting to see the cap weaken a bit across areas mainly along and west of the Laramie Range with the weakest cap across the mountain ranges. This area is only showing marginal cape values (<1000 j/kg) and weak shear 25-30kts. Dewpoints are also drying out a bit out a bit as well due the shallower moisture in place. Would not be surprised to see a few showers and thunderstorms develop in areas west of the Laramie Range during the next couple of hours with the main threat in this region being gusty wind speeds to 50 mph and small hail. Meanwhile, things are finally starting to clear out across the Nebraska Panhandle. This area has a very moist air mass in place along with steep mid level lapse rates in place and better shear (40-50kts) projected by the HRRR. With all that said, we should be in for active afternoon in the Nebraska Panhandle and portions of Goshen/Niobrara counties with the supercells containing large hail and damaging winds. Tornado threat looks to be rather minimal at this time, but we will have to keep an eye on the low level flow to see if it backs ahead of the progressive shortwave. && .SHORT TERM...(Today through Sunday night) Issued at 327 AM MDT Sat Aug 12 2017 Stratus and fog are becoming more widespread this morning along the Cheyenne Ridge and in the river valleys of the Nebraska Panhandle. HRRR shows the continued expansion of fog through the morning so followed these trends for this morning's forecast. Increased PoPs as well for over our northwest locations as radar shows some rain showers headed this way. Otherwise, should remain a pretty quite morning. The rest of the weekend looks pretty active with the potential for a few strong to severe storms in the afternoon and evening. For today, a leading impulse of Pacific origin will move over the forecast area midday ahead of the main upper low diving southeast over Montana and the Dakotas. Timing of both features between the models seems to be pretty close, however the associated sfc features vary somewhat in the models. The main sfc trough developing over our plains this morning looks to shift east quite a bit faster in the GFS than other models, which would push the main plume of moisture and instability east of our counties. The NAM, ECMWF, and other high res models agree on keeping the sfc trough further west during the day, oriented northeast to southwest from Sioux County down to Laramie County. Will side with the consensus of models. Ahead of the trough, SBCapes are progged to be 2000-3000 J/kg in spots with a weak cap that should erode through the afternoon hours. Ample midlevel forcing and sfc convergence along the trough will initiate storms by the mid afternoon, and bulk shear around 40 kts combined with rather large instability will support supercellular mode at least initially. However, increasing northwest flow in the wake of the upper impulse looks to contribute to an upscale in development as the storms push east across the Panhandle through the late afternoon and evening. Llvl shear progs are not all that impressive with sfc flow mainly out of the south, but there could be pockets of backed winds along terrain features which could increase llvl shear. Therefore, think the main threats from supercells will large hail (>1") and strong outflow winds (>60mph), but any areas that see those backed sfc winds certainly have the potential for a brief tornado as well. The main upper trough will move across the Dakotas tonight and will push a cold front across the northern half of the CWA. Models show it stalling from the northern Laramie Range to the southeast for tonight. A second impulse looks to approach from the southwest and trek across northern Colorado tonight as well, so we could see a few showers and weak storms continue overnight. Potential for fog will be much more sporadic across the region as convection disrupts the boundary layer somewhat. The upper ridge will move over the Rockies on Sunday with yet another midlevel impulse expected to move across the forecast area in the afternoon. The cold front is progged to remain quasi- stationary across our plains counties through the day, with southeasterly return flow bringing back the higher dewpoints especially in the Panhandle. Forecast soundings indicate the postfrontal airmass will modify rather quickly through the day so it's looking a good bet we'll be dealing with another day of severe thunderstorms along the WY/NE border and points east in the afternoon/evening. Further west, expect weaker thunderstorms to develop as the wave moves overhead along with breezy westerly sfc winds within unidirectional westerly flow. .LONG TERM...(Monday through Friday) Issued at 327 AM MDT Sat Aug 12 2017 Robust shortwave will move from the Great Basin into western WY on Monday afternoon. Surface trough will be in place over the plains with convective development likely in the afternoon especially along and north of a Douglas to Chadron line. Could see one or two strong storms again on Monday afternoon with the expected shear/instability in place. Pretty strong Pacific cold front passes across the area on Tuesday with showers and thunderstorms developing ahead of it in the afternoon. Strength of the forcing and tightening low level gradients may allow for strong winds with some of the more robust convection. Zonal flow sets up for Wednesday trending to more NW flow by Friday as ridging begins to try to rebuild over the western US. Looks like much of the low level moisture gets pushed east of our CWA by Wednesday with lessening chances for convection and seasonable temps. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1139 AM MDT Sat Aug 12 2017 MVFR cigs will continue for the next hour or two at SNY/AIA. Otherwise VFR conditions will prevail through the taf period. Scattered showers and thunderstorms will develop between 19-21Z across much of the region. A few of the storms could be strong to severe, mainly over the Nebraska Panhandle. Brief heavy rain, hail, and gusty winds will be possible with the stronger storms. && .FIRE WEATHER... Issued at 327 AM MDT Sat Aug 12 2017 Fire weather concerns will remain minimal through middle of next week with near normal temperatures and chances for showers and thunderstorms expected through this time. High pressure looks to build in from the west later in the week, bringing warmer and drier conditions back to the region. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && UPDATE...REC SHORT TERM...RJM LONG TERM...DEL AVIATION...ZF FIRE WEATHER...RJM
Hazardous Weather Outlook National Weather Service Cheyenne WY 346 AM MDT Sat Aug 12 2017 WYZ101>119-131000- Converse County Lower Elevations-Niobrara County- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-Central Laramie Range and Southwest Platte County- East Platte County-Goshen County-Central Carbon County- North Snowy Range Foothills-Southwest Carbon County- Sierra Madre Range-Upper North Platte River Basin-Snowy Range- Laramie Valley-South Laramie Range-South Laramie Range Foothills- Central Laramie County-East Laramie County- 346 AM MDT Sat Aug 12 2017 This hazardous weather outlook is for portions of east central Wyoming...south central Wyoming and southeast Wyoming. .DAY ONE...TODAY AND TONIGHT Scattered thunderstorms will develop by early afternoon over the Laramie Range and move east and southeast into the plains by mid afternoon. A few storms may become severe over eastern portions of Southeast Wyoming. Large hail and damaging winds will be the main threat. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Scattered thunderstorms will develop again on Sunday and Monday afternoons. A few strong storms with hail and gusty winds are possible both days. Thunderstorm chances will diminish through mid week. .Spotter information statement... Spotter activation may be needed this afternoon along and east of a line from Lusk to Torrington to Pine Bluffs. NEZ002-003-019>021-054-055-095-096-131000- Dawes-Box Butte-Scotts Bluff-Banner-Morrill-Kimball-Cheyenne- North Sioux-South Sioux- 346 AM MDT Sat Aug 12 2017 This hazardous weather outlook is for portions of western Nebraska. .DAY ONE...TODAY AND TONIGHT Scattered thunderstorms will develop and move east and southeast into the Panhandle by mid to late afternoon. Storms will continue into the early evening hours. A few storms may become severe with large hail and damaging winds being the main threat. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Scattered thunderstorms will develop again on Sunday and Monday afternoons. A few strong storms with hail and gusty winds are possible both days. Thunderstorm chances will diminish through mid week. .Spotter information statement... Spotter activation may be needed this afternoon and evening over the Nebraska Panhandle.
The Cheyenne radar (KCYS), 187 km away, was scanning. The volume nearest the first event began at 20:33 UTC.
7 hail, 1 thunderstorm wind. Local standard time, as filed.
Estimated wind gusts of 55 to 60 mph were observed.
Golf ball size hail was observed southwest of Hemingford.
Golf ball size hail was observed northwest of Alliance.
Golf ball size hail fell along Highway 385. Several vehicles sustained broken windshields.
Quarter size hail was observed south of Bushnell.
Ping pong ball size hail was observed north of Bridgeport.
Half dollar size hail covered Highway 385 south of Alliance.
Quarter size hail was observed northeast of Bridgeport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nebraska in 2017Every state in 2017This day in weather historyWarnings in Nebraska, August 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 712226, 712248, 712250, 712257, 712258, 712260, 712253, 712261.