An embedded shortwave within a longwave western US trough moved across the midwest, merging with a plume of increasing moisture transport out of the south. While no severe weather was reported, thunderstorms developed in the afternoon.
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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 DMX wrote it up.
An embedded shortwave within a longwave western US trough moved across the midwest, merging with a plume of increasing moisture transport out of the south. While no severe weather was reported, thunderstorms developed in the afternoon. Unfortunately one storm produced lightning that struck the Calhoun County court house and produced many thousands of dollars in damage.
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 Des Moines, IA wrote its last area forecast discussion before the first event at May 8, 1:16 PM CST, 4 hours 19 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 216 PM CDT Sat May 8 2021 .DISCUSSION.../Tonight through Saturday/ Issued at 216 PM CDT Sat May 8 2021 The forecast remains cool for the season, with intermittent rain and frost chances. Highlights: - Widespread rainfall forecast tonight into Sunday morning. - Sporadic rain chances from Monday through the work week, but low confidence and generally low coverage/amounts. - Unseasonably cool weather continues with frost possible in some parts of the forecast area Mon/Tue/Wed mornings. The first wave of the ongoing rainfall event moved through the service area this morning into early afternoon, and is still affecting our northern and eastern counties at this hour. Isolated thunderstorms were observed briefly this morning but lightning has sense ended for the most part. Interestingly, multiple showers/storms also produced very small ice pellets/hail during the morning to midday hours, prompting numerous reports. This was doubtless due to the unseasonably cool temperatures in the column and low freezing level. In wake of the first wave of rain much of the area will see a few hours of dry conditions this afternoon, excepting perhaps the far north, but then as a surface cyclone moves from Nebraska/Kansas to roughly along the Iowa/Missouri border tonight rain will fill back in, becoming more widespread and heavier than what we have seen today. With the center of the cyclone passing near or south of the border severe weather is not anticipated in our area, however additional thunderstorms are likely, though they will likely be widely scattered. Meanwhile, we should manage the most robust widespread precipitation amounts the state has seen in months, providing a very welcome, if limited, relief to nascent drought concerns. Made little change to QPF forecast overnight, with generally 1.0-1.5 inches forecast in any areas south of Highway 20, and 0.5-1.0 inches to the north. Most of this accumulation will come from this evening into the pre-dawn hours in a steady, soaking fashion. Given the antecedent conditions in place, there are no hydrological concerns of note. By Sunday afternoon the influence of a large high pressure dome building over the Great Lakes and Minnesota will begin to exert itself, pushing clouds and showers out to our south/southeast by the afternoon. This feature will then dominate our weather through midweek, providing several days of very cool May weather with light winds eventually coming around to southerly by Wednesday or so. A mid-level shortwave trough will move over Wisconsin and northeastern Iowa on Monday and provide lift sufficient to generate a few light showers across Iowa, however, with the dry/air subsidence in place below the forcing as evident in forecast soundings, it remains unclear how much convection will be able to occur and what coverage of rain actually reaching the surface would be...likely quite low. Have thus nudged POPs up to around 10-15 percent, holding mention out of the text forecast for now, but will continue to monitor this potential in subsequent updates. At any rate, any rain that does occur on Monday would have little to no impact as it would be spotty and very light. With high pressure dominating the region in the first half of the week we will see multiple opportunities for overnight/early morning frost, mainly in northern and eastern sections. However, this will be highly dependent on sky cover as there are also multiple opportunities for mid/high level clouds during this time. Thus will likely need to take a one-day-at-a-time approach with any frost potential and possible headlines. By the latter part of the coming week, a modest/flat ridge will attempt to build over the Rockies and transition eastward toward the Midwest and Iowa, providing a steady warming trend heading toward next weekend. However, various long-range models have been progging additional mid-level shortwave impulses riding over the top of the ridge and producing intermittent rain/storm chances near Iowa from around late Thursday or so onward. The predictability of any such features is very low at this range, so prolonged low POPs of 20-30 percent remain a standard feature of the outgoing extended forecast during this time frame. && .AVIATION.../For the 18Z TAFS through 18Z Sunday/ Issued at 1233 PM CDT Sat May 8 2021 Scattered light showers may affect the terminals briefly this afternoon, but any visibility or ceiling restrictions will be very transient and isolated. Otherwise, expect more widespread showers by around 00Z and through the night, with MVFR/IFR visibility and steadily lowering ceilings likely reaching IFR heights around FL007-009 by midnight. Have taken best estimate at timing these changes, but expect refinement and probably amendments this evening as the showers expand. Conditions will slowly but steadily improve during the day Sunday, with VFR prevailing by the afternoon && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && DISCUSSION...Lee AVIATION...Lee
Hazardous Weather Outlook National Weather Service Des Moines IA 248 PM CDT Sat May 8 2021 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-092000- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene- Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper- Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union- Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne- Appanoose-Davis- 248 PM CDT Sat May 8 2021 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Scattered thunderstorms will develop later this afternoon and continue overnight. Severe storms are not anticipated. .DAYS TWO THROUGH SEVEN...Sunday through Friday Patchy frost may be possible Monday and Tuesday mornings. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. Hagenhoff
The Des Moines radar (KDMX), 105 km away, was scanning. The volume nearest the first event began at 23:34 UTC.
1 lightning. Local standard time, as filed.
Emergency management reported a lightning strike to the the county court house, resulting in over 20,000 dollars in damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2021Every state in 2021This day in weather historyWarnings in Iowa, May 2021
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: 953733.