Thunderstorms initiated along the higher terrain of western South Dakota and moved eastward through a stout instability axis from 2000-2500 J/kg MUCAPE and deep-layer shear up to 40 knots. However, the storms quickly outran the better parameters and weakened moving into southeast South Dakota, but not before linear storms produced areas of 60 to 65 mph wind across Gregory County.
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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 FSD wrote it up.
Thunderstorms initiated along the higher terrain of western South Dakota and moved eastward through a stout instability axis from 2000-2500 J/kg MUCAPE and deep-layer shear up to 40 knots. However, the storms quickly outran the better parameters and weakened moving into southeast South Dakota, but not before linear storms produced areas of 60 to 65 mph wind across Gregory County. Additional storms developed several hours later during the early morning hours with isolated wind damage southeast of Huron.
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 Aug 13, 5:38 PM CST, 3 hours 34 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 638 PM CDT Wed Aug 13 2025 .KEY MESSAGES... - There is a Level 2 of 5 risk for severe thunderstorms tonight for areas west of Highway 281 and a Level 1 of 5 risk extending to the east near the I-29 corridor. The greatest risk for severe weather is from 10pm through 2am, with potential for wind gusts to 70 mph, half dollar size hail, and locally heavy rain. - High heat and humidity return Thursday through the weekend. Afternoon heat index values could approach or exceed 100 degrees, especially south of I-90 on Friday and Saturday. - An active weather pattern brings low chances (20-30 percent) for showers and thunderstorms late Thursday night through the weekend. Severe weather cannot be ruled out, but confidence in any details is low. && .DISCUSSION... Issued at 239 PM CDT Wed Aug 13 2025 TODAY: Current radar shows light showers and thunderstorms moving east-southeast north of Highway 14. These are expected to remain to the north but may move more southeasterly over Minnesota. GOES water vapor imagery shows a weak wave that is supporting these showers. While these are not expected to become severe they could produce isolated brief heavy rainfall and gusts to around 40 mph. Looking again at GOES water vapor imagery we can see the main shortwave of the day working its way east from south central Montana. This wave will initiate convection over the Black Hills that will move into central South Dakota between 10pm to 1am tonight. The majority of the CAMS agree with this timing, the outlier being the 12Z Nam Nest, which has backed off on convection overall. A moderately unstable environment will be in place as storms move in with MUCAPE around 1500-2500 J/kg, 30-40 kts of 0-6 bulk shear, and mid-level lapse rates around 7.5 C/km. However, a fairly stout cap will already be in place, and instability is expected to decrease as the night progresses. The greatest threat for strong to severe thunderstorms will be over central South Dakota where hail to the size of a half dollar, damaging wind gusts of 70 mph, and locally heavy rainfall are possible. The threat for tornadoes is low but cannot be ruled out, especially over south central South Dakota. This location is most likely to see deep shear vectors perpendicular to the forcing, with winds that are backing slightly, and therefore has the best chance for severe thunderstorms capable of producing tornadoes. As the storms move east I suspect they will transition from surface based to elevated and weaken as they progress toward the I-29 corridor between 2-5am. As they do so the threat will transition to damaging winds with gusts of 70 mph possible. There is also an increasing signal for a wake low to develop behind the storms. It may be that the wind threat will remain for an hour or two after storms have passed. THURSDAY: Showers may linger into mid-morning Thursday east of I-29 but things should dry out for the afternoon. Aloft a quasi-zonal pattern settles in for the next few days. Breezy southerly winds will help surface highs warm into the 80s to mid 90s. The warmest temperatures are expected west of the James River Valley. Southerly winds will also transport north higher dewpoints in the upper 60s to mid 70s. While the forecasted apparent temperatures remain mostly below Heat Advisory criteria, it will still be very hot and humid. Those who'll be outdoors need to use caution and ensure they are properly hydrated. Lows for Thursday will be warm, in the upper 60s to low 70s. Late Thursday night to early Friday morning a fast moving short wave will work through the pattern bringing a low chance (<30%) of rain. Mid-range guidance is not in good agreement on timing and coverage of showers and thunderstorms. They are in better agreement of a moderately unstable environment with a strong cap in place. The most likely scenario is some elevated showers will form east of I-29. One exception may be for portions of southwestern Minnesota where the cap is a bit weaker, and updrafts may be able to punch through to initialize convection. If they do, the greatest threat will be large hail and damaging wind gusts. FRIDAY-THE WEEKEND: For the rest of Friday, expect dry conditions as the southern portion of the jet stream pushes north and forms a ridge over the north central Plains. Another day of southerly winds, WAA, and moisture advection will lead to hot and humid conditions for Friday afternoon. Highs are expected to top out in the upper 80s to mid 90s. Heat index values will be in the upper 90s to low 100s, with the highest values along the southern Missouri River counties. We will continue to monitor the heat trends to determine if any heat headlines will be needed over the next couple days. Very little relief from the heat overnight with lows only falling to the upper 60s to 70s. Saturday will be similar to Friday with highs climbing to the mid 80s to mid 90s, with heat index values in the 90s to low 100s. The warmest conditions are expected south of I-90. Lows will again be warm, in the upper 60s and 70s. A weak boundary moves through the region Saturday into Sunday which will work to lower dewpoints to widespread 60s. Sunday highs will still be very warm, in the 80s to mid 90s. However, heat index values will remain less than 100 thanks to the lower dew points. Throughout the weekend, multiple low amplitude short waves work through the upper ridge bringing low chances (generally <30%) for rain and possibly thunderstorms. Guidance is in low agreement and so confidence in timing, location, and coverage of storms is low. We will provide updates as details become clearer. NEXT WEEK: For most of next week the upper ridge pattern looks to remain in place. Monday and Tuesday a series of short mid-level waves bring chances for showers and thunderstorms. Wednesday and Thursday look to remain mostly dry before shower chances return again Friday. Highs will be near normal for the most part in the upper 70s and 80s. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 632 PM CDT Wed Aug 13 2025 Showers and very isolated lightning continue to move east through 3z this evening along the US Hwy 14 corridor south toward KYKN. Further west, watching a line of storms in western SD move east through the late evening and overnight. Some of these storms may be strong to severe. Main threat will be after 3z through about 7z, and the line should weaken as it moves toward the I-29 and eastward. Did include PROB30 mentions of storms at all three sites, and expect further refinement this evening. Outside of convection, VFR conditions prevail. Winds out of the south/southeast with gusts around 25 knots through the period, which should preclude any LLWS. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...AJP AVIATION...SG
Hazardous Weather Outlook National Weather Service Sioux Falls SD 639 PM CDT Wed Aug 13 2025 SDZ038>040-050-052>070-142345- Beadle-Kingsbury-Brookings-Gregory-Jerauld-Sanborn-Miner-Lake-Moody- Brule-Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas- Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Clay- 639 PM CDT Wed Aug 13 2025 This Hazardous Weather Outlook is for central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Tonight. Scattered thunderstorms spread east into south central South Dakota later this evening. Isolated strong to severe thunderstorms are possible with the greatest threat between 10 PM and 2 AM. The strongest storms may produce hail up to half dollar size, wind gusts up to 70 mph, and locally heavy rainfall. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Hot, humid weather may push afternoon heat index readings to around 100 degrees Friday and Saturday, especially south of the Interstate 90 corridor. Periodic chances for thunderstorms return Friday night through the weekend, but there is low confidence in details such timing and severe weather threat at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed. IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ071-142345- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Union- 639 PM CDT Wed Aug 13 2025 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska and southeast South Dakota. .DAY ONE...Tonight. Scattered showers and thunderstorms may spread east overnight into early Thursday morning, but severe weather is unlikely. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Hot, humid weather may push afternoon heat index readings to around 100 degrees Friday and Saturday, especially south of the Interstate 90 corridor. Periodic chances for thunderstorms return Thursday night through the weekend, but there is low confidence in details such timing and severe weather threat at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The North Platte radar (KLNX), 159 km away, was scanning. The volume nearest the first event began at 03:10 UTC.
4 thunderstorm wind, 1 high wind. Local standard time, as filed.
Thunderstorm winds, which gusted as high as 60 mph, were measured by South Dakota Mesonet station GGMS2 Gregory 7SSW.
Thunderstorm wind gusts as high as 62 mph were measured by a personal weather station.
Thunderstorm wind gusts as high as 58 mph were measured by South Dakota Mesonet station ACMS2 Academy 3NNW.
Dissipating showers led to the development of locally enhanced non-thunderstorm wind gusts up to 61 mph at a site 5 miles east-southeast of Tyndall.
Thunderstorm winds heavily damaged a south side barn door and roof.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2025Every state in 2025This day in weather historyWarnings in South Dakota, August 2025
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: 1290505, 1290506, 1290507, 1290508, 1290501.