74 inches of rainfall at Worthington during the afternoon of June 18.
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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.
With deep moisture resulting in around 1.75 inches precipitable water, slow-moving thunderstorms along a cold front brought 2.74 inches of rainfall at Worthington during the afternoon of June 18.
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 18, 1:40 PM CST, 2 hours 2 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 240 PM CDT Thu Jun 18 2020 .SHORT TERM...(This Evening through Friday) Issued at 240 PM CDT Thu Jun 18 2020 18.19Z observational analysis shows a surface cold front from roughly Marshall to Sioux Falls to Yankton. Along this front is a band of showers and embedded thunderstorms. So far, there has been no severe weather with mainly periods of moderate to heavy rain and occasional lightning. This area of showers and storms will continue east-northeast through the afternoon and early evening before exiting the forecast area sometime after 19.03Z. Best chances for any strong to severe storms this afternoon looks to be across northwest Iowa into adjacent portions of far southwest Minnesota where some clearing has allowed the mid-level CAP to erode and CAPE to build up to 1500 J/kg. 0-1 km and 0-6 km shear is weak, but a few stronger updrafts could result in marginally severe hail and strong wind gusts. Bigger concern is heavy rain. With PWATs from 1.5 to 1.7 inches and rain rates of 1-2 inches per hour, could see some localized ponding or flooding of low lying areas, especially in urban areas. Overall, flood concern is low given forward speed of storms and dry antecedent conditions. Skies will clear from west to east overnight and with light wind and a cooler post-frontal airmass, expect nighttime lows mainly in the 50s. Friday will be partly sunny and dry as quick-moving surface high pressure drifts across the region. It will also be noticeably more comfortable with highs near normal (upper 70s to lower 80s) and dewpoints in the lower to mid 50s. .LONG TERM...(Friday Night through Thursday) Issued at 240 PM CDT Thu Jun 18 2020 Southwest flow aloft continues on Saturday with a short-wave rounding the base of the southern Canadian prairies trough. A surface boundary stretches from KS to northwest MO and into central IA keeping the heat/moisture and best chances for stronger storms well south of the forecast area. Will still carry chance POPs on Saturday for much of the area as most model solutions develop some showers and storms with wrap around moisture. Skies will initially be more cloudy than not, but should see some gradual clearing. Expect highs in the mid to upper 70s. Sunday through the middle of next week...18.12Z GFS/ECMWF show a closed low over central Manitoba slowly wobble to the southeast and across southern Ontario. This keeps the forecast area in quasi-zonal/northwest flow aloft with a series of weaker short waves moving through. Because of this, most days have at least 20-30 POPs and given the pattern, this seems reasonable. More dry periods than wet are likely, so will need to fine-tune POPs over the coming days as confidence increases. Temperatures are likely to be near seasonal averages with daytime highs in the upper 70s to lower 80s and nighttime lows mid 50s to mid 60s. The exception being Sunday when 925 hPa temperatures increase to between 21 and 22 Celsius, which could push afternoon highs into the mid-upper 80s. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 629 AM CDT Thu Jun 18 2020 Borderline MVFR cloud ceilings are across the western area, with the cold front producing scattered rain showers and thunderstorms throughout the TAF period. As of 1130Z, the front is oriented along a line from Brookings SD, to Mitchell, SD to Yankton, SD and is moving eastwards. Expect southerly winds until the front moves through, at which point the winds will turn northwesterly. The cold front will pass through the southern I-29 corridor by around noon, and will keep rain and thunderstorm chances through the afternoon. Winds decrease significantly overnight, remaining north- northwesterly, with some models suggesting fog could form overnight but there is very low confidence in that occurring. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...Rogers LONG TERM...Rogers AVIATION...APT
Hazardous Weather Outlook National Weather Service Sioux Falls SD 642 AM CDT Thu Jun 18 2020 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-191145- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock- 642 AM CDT Thu Jun 18 2020 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa and southwest Minnesota. .DAY ONE...Today and tonight. Chances for strong to severe thunderstorms are possible this afternoon across NW IA and SW MN, with damaging winds being the main threat. Best time range for storms will be from 3 PM through 7 PM this evening. While unlikely, there is a slight chance for flash flooding with these storms today. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. NEZ013-014-SDZ038>040-050-052>071-191145- Dixon-Dakota-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- Union- 642 AM CDT Thu Jun 18 2020 This Hazardous Weather Outlook is for 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...Friday through Wednesday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Sioux Falls radar (KFSD), 91 km away, was scanning. The volume nearest the first event began at 21:39 UTC.
2 flash flood. Local standard time, as filed.
Up to two feet of water was reported over Marine Avenue near the high school.
One vehicle became stalled in high water, with six reports of street flooding in the city. Property damage costs are rough estimates.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Minnesota in 2020Every state in 2020This day in weather historyWarnings in Minnesota, June 2020
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: 905614, 905615.