Thunderstorms developed along a nearly stationary pre-frontal boundary during the early evening across south central South Dakota. As cold pool development forced storms eastward off the initiating boundary into an environment with appreciable DCAPE and deep-layer shear of 40 to 50 knots, thunderstorms organized into a small bowing segment which plowed east and southeast with up to nearly 90 mph…
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The episode as NWS FSD wrote it up.
Thunderstorms developed along a nearly stationary pre-frontal boundary during the early evening across south central South Dakota. As cold pool development forced storms eastward off the initiating boundary into an environment with appreciable DCAPE and deep-layer shear of 40 to 50 knots, thunderstorms organized into a small bowing segment which plowed east and southeast with up to nearly 90 mph winds. After several hours, storms moved into a less favorable environment with both lesser shear and instability toward the James River Valley and weakened.
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 Jun 27, 11:22 PM CST, 1 hour 15 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 1222 AM CDT Sat Jun 28 2025 .KEY MESSAGES... - Strong to severe storms are possible this evening west of I-29, with initial development across south central South Dakota. Large hail to 2 inches and wind gusts to 70+ mph are the main threats. An isolated tornado cannot be ruled out. - Additional strong to severe storms are possible Saturday and Sunday during the afternoon/evening hours. Though each day's storm threat will be determined by the previous day's storms. Continue to monitor the forecast if you have outdoor or travel plans. - Warming temperatures and increasing humidity this weekend bring a risk of heat indices near 100F in some areas Saturday afternoon. Otherwise seasonably warm temperatures prevail much of next week. && .DISCUSSION... Issued at 251 PM CDT Fri Jun 27 2025 Quiet conditions persist through the first half of the afternoon hours today. However, things will change over the next few hours as thunderstorms develop along a boundary across south central South Dakota. These storms may be capable of large hail up to about 2 inches in diameter as the storm mode will be discrete during initial development. Storms look to quickly grow upscale into a mesoscale convective system (MCS) as they push eastwards which will transition the threat from large hail to damaging winds. Given steep low level lapse rates, and very high DCAPE values exceeding 1,500 J/kg, damaging winds to 70+ mph will then be the main threat. This damaging wind threat looks to be the main hazard for the forecast area though the large hail threat will coincide with it if a discrete storm can develop ahead of the line. At the same time, there could be an isolated tornado as well with 0-3 km shear vectors with magnitudes of about 25 knots oriented perpendicularly off the MCS. Once the storms push into and east of the Missouri River Valley, they should weaken with eastward extent as capping will strengthen via nocturnal stabilization. The low level jet will also be strengthening during this period of time as well. That said, this cap will not be moist and lifting will above the cap results in little to no instability. Thus, think that if any showers or storms persist through tonight, they will not be severe. Overnight low temperatures will fall to the 60s. Severe weather chances continue through Saturday though there remains uncertainty in this potential. The general consensus for severe storms amongst the 12z guidance is for storms to develop along the warm front but the location of this front is driving the uncertainty. The front looks to end up just northeast of the area. However, this can still change depending on how tonight's storms shake out. With mean flow paralleling the boundary, storms look to quickly grow upscale into a line. At the same time, a stout elevated mixed layer (EML) will be in place with mid level lapse rates approaching 9C/km. This will present large capping across the forecast area and could inhibit convection to a large degree. The main question will be if diurnal heating will be strong enough to mix out the cap. While high temperatures will reach into the upper 80s and 90s across the area, questions still remain if highs will warm a bit more to potentially the mid to upper 90s or even low 100s. However, both the REFS and HREF show a near 0% chance for highs to exceed 100F. IF storms are able to develop, they would likely be in a line spanning back from the previously mentioned boundary down the dry line. Large hail will be possible with initial updrafts but quick upscale growth will quickly transition the main hazard from large hail to damaging winds. To account for this potential, did keep broad chance PoPs across the area. The other aspect to Saturday is that it is going to be hot and humid. With highs warming to the upper 80s and 90s while dew points moisten to the 60s and 70s, heat indices will be up into the 90s to nearing 100F. Did think about issuing heat headlines but given how borderline the environment is, decided to hold off on issuing headlines at this time. Will continue to monitor this potential. Low temperatures will fall to the mid to upper 60s overnight. Severe threat looks to continue into Sunday though this looks be a more isolated threat. This potential will be contingent on how fast the boundary is able to push out of the area. Per the GFS, Canadian, and Euro ensembles, the front looks to be pushing just southeast of the area during the early to mid afternoon hours. This looks to keep convection just out of the area. This is supported by the NBM as it shows the highest probabilities for exceeding a tenth of an inch of rain off to the southeast. Will still monitor the potential for convection to develop earlier than currently anticipated though. Outside of rain and storm chances, Sunday will be a cooler day with highs only warming to the 80s with northerly winds keeping a light breeze in place. Lows will fall to the 60s overnight. Next week looks to begin on the dry side as the shortwave responsible for the end of week and weekends storms will push east of the region. This will keep high temperatures near to just above normal for this time of year in the 80s to low 90s. Upper level ridging over the southern CONUS could result in ridge riding shortwaves that may bring storm chances back to the Northern Plains. However, too far out to say for sure about any details just yet. Will continue to monitor this potential. Aside from rain chances, highs will remain in the && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1213 AM CDT Sat Jun 28 2025 Scattered convection continues to move through eastern South Dakota early this morning. Within thunderstorms, drops to MVFR/IFR visibility is possible, with CIGs near 3k ft AGL. Into mid-morning, the greatest convection risks will continue near or north of Highway 14, with skies clearing further south. A frontal boundary sets up over eastern South Dakota, with isolated to scattered convection forming along this boundary after 4-5pm. Highly uncertain on the eventual track of this convection into the evening, so will continue to remain with PROB30 groups at all TAF locations. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...Meyers AVIATION...Dux
Hazardous Weather Outlook National Weather Service Sioux Falls SD 637 PM CDT Fri Jun 27 2025 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ038>040-050-052>071-282345- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory- Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook- Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton- Union- 637 PM CDT Fri Jun 27 2025 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Tonight. Showers and thunderstorms return to the region this evening through tonight. Some storms may be strong to severe, especially in areas west of Interstate 29. Main threats are large hail to 2 inches with initial storms, transitioning to wind gusts up to 70 mph as storms evolve into a line. A tornado cannot be ruled out. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Additional periods of showers and thunderstorms are expected into the weekend. Some storms may become severe Saturday afternoon and evening and again Sunday. Details remain uncertain for Saturday and Sunday. Stay weather aware, especially if you have outdoor plans. Heat and humidity briefly returning to the area Saturday may push heat indices into the 95 to 105 degree range during the afternoon. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Preliminary Local Storm Report
National Weather Service Sioux Falls SD
1100 PM CDT Fri Jun 27 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1043 PM Tstm Wnd Gst 4 N Olivet 43.30N 97.68W
06/27/2025 M83 MPH Hutchinson SD Public
Roof-mounted weather station measured an
83.1 mph wind gust.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
1111 PM CDT Fri Jun 27 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1045 PM Tstm Wnd Gst 3 S Scotland 43.10N 97.72W
06/27/2025 M51 MPH Bon Homme SD Public
Via personal weather station.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
1113 PM CDT Fri Jun 27 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1040 PM Tstm Wnd Gst 2 WNW Scotland 43.16N 97.76W
06/27/2025 M54 MPH Bon Homme SD Public
Via personal weather station.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
1141 PM CDT Fri Jun 27 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1119 PM Tstm Wnd Gst 4 WSW Yankton 42.86N 97.46W
06/27/2025 M64 MPH Yankton SD Public
Via personal weather station.
&&
akPreliminary Local Storm Report
National Weather Service Sioux Falls SD
1150 PM CDT Fri Jun 27 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1143 PM Hail Yankton 42.89N 97.39W
06/27/2025 M0.75 Inch Yankton SD Public
&&Preliminary Local Storm Report
National Weather Service Sioux Falls SD
1248 AM CDT Sat Jun 28 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1241 AM Hail 4 SW Utica 42.94N 97.55W
06/28/2025 M1.00 Inch Yankton SD Trained Spotter
Pea to quarter size hail lasted 15 minutes.
Time estimated from radar.
&&
JHThe Sioux Falls radar (KFSD), 120 km away, was scanning. The volume nearest the first event began at 06:36 UTC.
1 hail. Local standard time, as filed.
Observed hail was pea to nickel size, although most hailstones were the size of dimes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
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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: 1278623.