A strong thunderstorm developed along a frontal boundary in the presence of 40 knots of deep-layer shear, which resulted in a briefly rotating storm producing marginally large hail.
Every event with a place to put it. Tap one for its entry below.
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 FSD wrote it up.
A strong thunderstorm developed along a frontal boundary in the presence of 40 knots of deep-layer shear, which resulted in a briefly rotating storm producing marginally large hail.
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 Sioux Falls, SD wrote its last area forecast discussion before the first event at Jul 25, 5:12 PM CST, 1 hour 7 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 612 PM CDT Sun Jul 25 2021 .SHORT TERM...(This Evening through Monday Night) Issued at 246 PM CDT Sun Jul 25 2021 Spotty convective chances are the main challenge for the near-term. On the larger scale, we have an area of low pressure in western SD, with a weak boundary extending east-northeast into northeast SD. Meanwhile, a subtle upper level wave is seen in water vapor entering the western Dakotas. This wave may interact with the boundary by early evening, bringing a small chance of storms into our northwest this evening, and if this occurs, inverted-V soundings and DCAPE values above 1000J/kg would support an isolated strong wind threat. Slightly greater potential for a few storms appears to be in far north to northeast portions of the forecast area later tonight, as a modest southwesterly low level jet develops across the area. Nose of the jet focused near/northeast of the Buffalo Ridge, and will carry higher pops for the overnight period in this area. DCAPE values not quite as strong with this activity, but still quite a deep layer of dry sub-cloud air to accelerate the low level jet to the surface, so an isolated strong wind threat will continue. The convective forecast becomes more muddled for Monday, dependent on whether activity linger across northeast portions of our forecast area into the later morning hours, as depicted by several HRRR runs today. Tend to think this projection is overdone, as the waning LLJ convergence should be pushing off to the northeast, so have trended pops downward through the morning hours. Could still be a few weak boundaries lingering from overnight convection, but diurnal mixing should reestablish a primarily southerly flow across the forecast area, with consensus showing the main warm front again from central SD into central MN by late Monday into Monday night. Cannot totally rule out a few stray storms into southwest MN Monday night, but as with later tonight, think main focus for activity will be off to our north/northeast. Aside from these uncertain convective chances, the next 24-36 hours will feature modest humidity levels with dew points largely in the 60s tonight through Monday night. Abundant smoke aloft as indicated by HRRR Smoke model will have a continued impact on high temps, and have nudged readings for Monday down a few degrees from previous forecast. .LONG TERM...(Tuesday through Sunday) Issued at 246 PM CDT Sun Jul 25 2021 Heading into midweek, Tuesday-Wednesday continue to look like our period of greatest concern with regard to excessive heat/humidity. Very strong upper ridge builds into the northern Plains, with both NAEFS and ECMWF ensembles depicting 500mb heights across eastern SD/northeast NE near the highest in the climatological period by early Wednesday morning. Heat begins to build into our western CWA in earnest on Tuesday, before extending eastward on Wednesday as the thermal ridge is flattened by an approaching cold front. Low level temperature projections support highs in the mid 90s to low triple digits, though question remains if we mix high enough to attain these temperatures, how will the dew points respond. With evapotranspiration nearing its peak, overnight/morning dew points in the upper 60s to lower 70s seem reasonable. But soundings show plenty of dry air aloft, so suspect these may drop off a bit more than indicated. Confidence not quite high enough to adjust these values 2-3 days out, but will be something to consider in later forecasts. Almost certainly will see some variety of excessive heat headlines for these days, but given the uncertainty in dew points/humidity levels, still unsure whether that headline will be an advisory or warning. Relief comes in Wednesday night through the end of the week, as the upper ridge is flattened in response to a stronger jet diving southeast from the Canadian Prairies into the western Great Lakes. Transition to northwest flow may bring a somewhat more active pattern for the latter half of the week, with temperatures cooling off to much closer to normal && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 611 PM CDT Sun Jul 25 2021 Scattered showers and thunderstorms are currently over south-central SD, with activity expected to build over central SD and move eastwards. Most likely affecting the HON terminal between 0100-0400 UTC, with non-convective LLWS possible afterwards until around 0900 UTC due to a strong LLJ. Storms will continue traversing central SD into southern MN into the overnight period. Once winds pick up again in the morning, expect a predominantly southerly direction with gusts in the 15-25 mph range. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...JH LONG TERM...JH AVIATION...APT
Hazardous Weather Outlook National Weather Service Sioux Falls SD 453 AM CDT Sun Jul 25 2021 MNZ071-072-097-SDZ038>040-052>058-261000- Lincoln-Lyon-Pipestone-Beadle-Kingsbury-Brookings-Jerauld-Sanborn- Miner-Lake-Moody-Brule-Aurora- 453 AM CDT Sun Jul 25 2021 This Hazardous Weather Outlook is for southwest Minnesota, central South Dakota, east central South Dakota and south central South Dakota. .DAY ONE...Today and tonight. Isolated thunderstorms may develop this evening. Some storms could become strong to severe with damaging winds. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Much above normal temperatures will build into the area on Tuesday and Wednesday. Afternoon heat indices could be as high as 100 to 110 on those days. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed early tonight. IAZ001>003-012>014-020>022-031-032-MNZ080-081-089-090-098-NEZ013-014- SDZ050-059>071-261000- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Murray-Cottonwood-Nobles-Jackson-Rock-Dixon- Dakota-Gregory-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas- Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Union- 453 AM CDT Sun Jul 25 2021 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Much above normal temperatures will build into the area on Tuesday and Wednesday. Afternoon heat indices could be as high as 100 to 110 on those days. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Aberdeen radar (KABR), 117 km away, was scanning. The volume nearest the first event began at 00:16 UTC.
3 hail. Local standard time, as filed.
Hail was mostly pea size, but there were a few stones up to ping-pong ball size.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2021Every state in 2021This day in weather historyWarnings in South Dakota, July 2021
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: 977460, 977461, 977462.