97 inches near Spencer. Runoff resulted in minor flooding along the Ocheyedan River.
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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.
Rainfall between May 23 and May 27 totaled 2.22 inches 3 miles west northwest of Everly and 1.97 inches near Spencer. Runoff resulted in minor flooding along the Ocheyedan River.
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 May 26, 5:48 PM CST, 2 hours 42 minutes earlier.
AREA FORECAST DISCUSSION National Weather Service Sioux Falls SD 648 PM CDT Tue May 26 2020 .SHORT TERM...(This Evening through Wednesday) Issued at 236 PM CDT Tue May 26 2020 Vorticity maxima lifting northward out of southwestern Iowa has assisted in developing convection across much of central Iowa at mid- afternoon. Further northwest, light rain persists along I-29 and areas further east into Minnesota and Iowa. We'll be keeping a close eye on an inverted trough beginning to form just southeast of the forecast area. Latest observations support this trough residing just east of Storm Lake, with model guidance indicating this front may stall along the far eastern tier of counties by mid-late afternoon. MLCAPE values east of this boundary may climb up towards 1000 J/KG, with enhancement in 0-1 helicity along the boundary. While shortwave energy will favor pushing convection further more north and east during the afternoon, it's not inconceivable to have a storm to two drift further west and interact with this boundary. While the overall severe weather risks remains on the lower end, the greatest threat would come from a brief tornado and marginal hail. The greatest risk timeframe would be from 3pm to 5pm. Tonight: Most of the area remains dry tonight, outside of a narrow corridor where lingering showers may persist along a Storm Lake to Spencer line into the overnight hours. Light winds may lead to minor fog development further west, but this may be tempered by increasing cirrus. Wednesday: Wednesday again should remain dry as the forecast area remains stuck between in the weak flow between a stronger northern stream jet over the Canadian border and the upper low across Arkansas. Latest guidance continues to hint that weak surface convergence will stay southeast of the forecast area and this should keep any meaning shower chance out of the forecast area. .LONG TERM...(Wednesday Night through Tuesday) Issued at 236 PM CDT Tue May 26 2020 Thursday: More dominate northerly flow aloft will nudge southward early Thursday morning. A few lingering showers may move into the Missouri River valley Thursday morning but are expected to weaken and diminish after daybreak. Temperatures Thursday will climb into the lower 70s. Friday: High pressure moving through the region, along with a prevailing northwesterly flow at the low and mid-lvls will keep dry conditions around for Friday. Temperatures remain in the 70s. Saturday: GFS/EC both rather consistent on a subtle shortwave moving southeast early Saturday morning. Warm advection induced by this shortwave will produce showers and perhaps even isolated thunderstorms through the Missouri River valley. Northerly winds through the day will keep high temperatures on the cool side again, with highs stuck in the 60s. Sunday-Tuesday: Mid-lvl heights begin to rise quickly on Sunday and into next week, which should signal a rise to above normal temperatures for much of the region as we finish May and start June. Confidence increased for this pattern shift, as no strong blocking is expected to develop to prevent heights from rising further east in the CONUS. Highs will rise into the 80s into the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM CDT Tue May 26 2020 Cloud cover will slowly decrease from west to east over the next 24 hours. Although clouds will clear for areas west of I-29 overnight, fog is not expected to become a major issue because areas that see clearing skies will also have a drier air mass in place. Places that remain in the moist air mass east of I-29 will retain thick low to mid-level clouds, which reduces radiational cooling and prevents fog from becoming thick there as well. Light northerly to northwesterly winds develop Wednesday morning and continue throughout the day. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && SHORT TERM...Dux LONG TERM...Dux AVIATION...VandenBoogart
Hazardous Weather Outlook National Weather Service Sioux Falls SD 436 AM CDT Tue May 26 2020 IAZ001-012-020-031-MNZ071-072-080-089-097-098-NEZ013-014-SDZ038>040- 050-052>071-270945- Lyon-Sioux-Plymouth-Woodbury-Lincoln-Murray-Nobles-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-Clay-Union- 436 AM CDT Tue May 26 2020 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...Today and tonight. Patchy fog is possible through mid-late morning. Widespread fog is not expected. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. IAZ002-003-013-014-021-022-032-MNZ081-090-270945- Osceola-Dickinson-O'Brien-Clay-Cherokee-Buena Vista-Ida-Cottonwood- Jackson- 436 AM CDT Tue May 26 2020 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa and southwest Minnesota. .DAY ONE...Today and tonight. Patchy fog is possible through mid-late morning. Widespread fog is not expected. Scattered thunderstorms are expected to develop this afternoon into early evening. While the severe weather threat is low; some storms could become strong with gusty winds, small hail and lightning. Brief and weak funnel clouds will also be possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement National Weather Service Sioux Falls SD 455 PM CDT Tue May 26 2020 IAZ014-021-022-032-270200- Clay-Cherokee-Buena Vista-Ida- Including the cities of Spencer, Cherokee, Storm Lake, Ida Grove, Holstein, and Battle Creek 455 PM CDT Tue May 26 2020 Scattered thunderstorms forming along a weak boundary...situated across portions of northwestern Iowa...may produce brief funnel clouds. Any funnel clouds that develop are expected to be weak and not touch the ground. However if you feel your safety is threatened please seek shelter.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Ocheyedan River near Spencer (gage site SPOI4) crested 0.55 feet above flood stage on May 27. Agricultural land west of Spencer was flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyWarnings in Iowa, May 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: 886482.