Increased releases from upstream reservoirs to route heavy spring runoff downstream contributed to minor flooding between Fort Randall and Gavins Point Dam.
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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.
Increased releases from upstream reservoirs to route heavy spring runoff downstream contributed to minor flooding between Fort Randall and Gavins Point Dam.
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 31, 9:31 PM CST, 2 hours 29 minutes earlier.
Area Forecast Discussion National Weather Service Sioux Falls SD 1031 PM CDT Tue Jul 31 2018 .SHORT TERM...(This evening through Wednesday) Issued at 333 PM CDT Tue Jul 31 2018 Upper level trough has migrated east towards the Mississippi River Valley as upper level ridge expands across the west. This has resulted in temperatures warming across the region a few degrees over yesterday. Southwest flow will increase tonight ahead of a cold front approaching from the northwest. The increasing cloud cover along with the increasing winds will keep temperatures a shade warmer than the last few nights. Boundary appears to be a bit faster than models previously suggested, so am only expecting a passing shower or storm mainly in the morning hours. Capping inversion behind the front appears to limit convective chances across the east through the afternoon hours, so have limited convective chances to slight chance across northwest Iowa. .LONG TERM...(Wednesday night through Tuesday) Issued at 333 PM CDT Tue Jul 31 2018 Should see some nice radiative cooling across the area Wednesday night and have sided towards cooler guidance numbers with high pressure across the Upper Midwest. Warmer more muggy conditions are expected to develop Thursday into Friday as flow turns southerly. A series of short waves are expected to approach from the southwest late in the day leading to thunderstorm development across central South Dakota. As storms work east, instability becomes increasingly elevated and shallow, and expected storms to weaken. Additional storms are possible through the weekend as a series of waves move through in zonal flow. Models suggest on a strengthening upper ridge across the western US next week, but the location differs. The ECMWF strengthens across the western plains, while the GFS is situated further to the west. Both solutions would place the northern plains in northwest flow. There is likely to be an embedded shortwave or two in the flow, but timing is very inconsistent. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1031 PM CDT Tue Jul 31 2018 Quickly decaying line of showers near KHON should continue to fade as it moves southeast. Meanwhile, a cold front will continue to make its way through the region tonight and into Wednesday, switching winds to a more northerly direction as it does so. Mid level clouds will also be present through portions of the TAF period. Can't completely rule out a stray shower or MVFR ceiling as the boundary passes, but chances and confidence at any one site are too low to include in the TAF. Overall, predominantly VFR conditions are expected. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && SHORT TERM...BT LONG TERM...BT AVIATION...Kalin
Hazardous Weather Outlook National Weather Service Sioux Falls SD 424 AM CDT Tue Jul 31 2018 IAZ012-020-021-031-032-NEZ013-014-SDZ038>040-050-052>071-011000- Sioux-Plymouth-Cherokee-Woodbury-Ida-Dixon-Dakota-Beadle- Kingsbury-Brookings-Gregory-Jerauld-Sanborn-Miner-Lake-Moody- Brule-Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas- Hutchinson-Turner-Lincoln SD-Bon Homme-Yankton-Clay SD-Union- 424 AM CDT Tue Jul 31 2018 This Hazardous Weather Outlook is for portions of northwest Iowa, west central Iowa, northeast Nebraska, central South Dakota, east central South Dakota, 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...Wednesday through Monday Friday through this weekend, increased moisture and warmth, combined with supportive forcing aloft, could lead to some stronger thunderstorms in the region. There is low confidence in timing and threat details at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. IAZ001>003-013-014-022-MNZ071-072-080-081-089-090-097-098-011000- Lyon IA-Osceola-Dickinson-O'Brien-Clay IA-Buena Vista-Lincoln MN- Lyon MN-Murray-Cottonwood-Nobles-Jackson-Pipestone-Rock- 424 AM CDT Tue Jul 31 2018 This Hazardous Weather Outlook is for portions of northwest Iowa and southwest Minnesota. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Thunderstorms are possible Wednesday afternoon and evening. In addition to lightning, some storms could produce small hail and wind gusts of 30 to 50 mph. Friday through this weekend, increased moisture and warmth, combined with supportive forcing aloft, could lead to some stronger thunderstorms in the region. There is low confidence in timing and threat details at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
5 flood. Local standard time, as filed.
Other than a brief period from August 20 to August 23, minor flooding of mainly agricultural areas persisted through the entire month along the Missouri River near Greenwood (gage site GRWS2). The river remained in minor flood through the end of the month.
Minor flooding of mainly agricultural areas occurred as the Missouri River near Verdel (gage site MRVN1) remained above flood stage for most of the month. The river crested 0.4 feet above flood stage on August 16, but dropped briefly below flood stage from August 20 to August 23. The river remained in minor flood through the end of the month.
Minor flooding of mainly agricultural areas occurred as the Missouri River near Verdel (gage site MRVN1) remained above flood stage for most of the month. The river crested 0.4 feet above flood stage on August 16, but dropped briefly below flood stage from August 20 to August 23. The river remained in minor flood through the end of the month.
Bottom Road near Springfield was inundated and minor flooding of mainly agricultural areas occurred during the entire month as the Missouri River at Niobrara (gage site MRNN1) crested 1.2 feet above flood stage on August 17. The river remained in minor flood through the end of the month.
Bottom Road near Springfield was inundated and minor flooding of mainly agricultural areas occurred throughout the month as the Missouri River at Springfield (gage site SPGS2) crested 1.5 feet above flood stage on August 17. The river remained in minor flood through the end of the month.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in South Dakota in 2018Every state in 2018This day in weather historyWarnings in South Dakota, August 2018
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: 779524, 779802, 779803, 779804, 779805.