A cluster of thunderstorms developed over northwest to west central Iowa late in the evening of June 16th, strengthening on the nose of warm air advection and the low level jet. The initial discrete cell was able to produce up to ping pong balled sized hail.
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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.
A cluster of thunderstorms developed over northwest to west central Iowa late in the evening of June 16th, strengthening on the nose of warm air advection and the low level jet. The initial discrete cell was able to produce up to ping pong balled sized hail. As the cluster developed further into a small bowing segment, damaging wind gusts became more prevalent.
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 Jun 16, 6:02 PM CST, 2 hours 7 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 702 PM CDT Wed Jun 16 2021 ...Updated Aviation Discussion... .DISCUSSION.../Tonight through Wednesday/ Issued at 258 PM CDT Wed Jun 16 2021 Take Home Points: *Hot tomorrow/Thursday - HI approaching 100-105 deg F for C/W/S IA *Scant chances for storms tonight, severe threat remains Thursday PM *Best widespread precipitation opportunity remains Sunday, uncertain chances next week Discussion: Overall it was another quiet day across the area with only a few mid to high level clouds stream across the area this afternoon. With the thermal ridge remaining centered west of the state, the hottest temperatures remained mostly W of the Missouri River, but will arrive in earnest tomorrow. Highs today remain on track to reach the upper 80s E to the mid 90s deg F. W and will remain tolerable with dew points mostly in the 50s to low 50s deg F. Looking into the forecast, let us start with temperatures. Thursday will be the hottest day of the forecast period and hottest day of the season for that matter. Thermodynamically, the pieces will be in place, including 850mb temps into the mid 20s, modest SW flow, and likely ample sunshine. That last item touches on a caveat that could prevent some areas from reaching into the upper 90s to low 100s. Anticipated scattered convection tonight may fester into the morning and resulting debris clouds could delay peak heating and suppress MaxTs a couple of degrees. Currently do not anticipate overnight convection to be a major issue with best chances to the E of areas with the best heat setup. More on the convection potential latter though. As it sits, Widespread upper 90s/around 100 deg F MaxTs are forecast from roughly Ames/Des Moines and areas to the S and W. Another note, models have struggled with Td, too moist, which lends to the forecast continuing to reside around the 75th percentile in model certainty. It is also possible the forecast remains a degree or two too low, especially if convection is a non-issue and Tds remain lower than forecast. Regardless, it will be hot and have gone with a heat advisory in the above mentioned area with heat index values around 100 to 105 deg F expected. Please take the necessary precautions if working or enjoying the outdoors for any prolonged periods of time. After Thursday, conditions ease a bit but remain on the warmer end of normal for this time of the year as large scale flow turns northwesterly to zonal. Additional cooling should be seen later Sunday on the heels of a frontal passage. Turning to shower/storm/precipitation, there remain multiple opportunities in the forecast but many areas of the state may not receive substantial relief to current dry and drought conditions. Tonight, theta-e advection ahead of the surface boundary will continue and in conjunction with the LLJ should spark some convection. Unfortunately, the warm mid-levels may prevent much activity from initiating in the area and may end up relying on storms in MN streaming S. The threat for severe remains low, but elevated storms with dry low levels would suggest damaging winds as the primary threat and hail secondary. Activity should wane in the morning hours and clear out/yield sunshine for the hot day Thursday. For Thursday afternoon/Thursday night, there remains a SPC Slight Risk for portions of central into northern and northeast IA. Perusing forecast sounding, consistency remains in quite a large cap to overcome throughout the forecast area. The cap is less robust as you work into S MN, and will be the likely location for initial convection in the mid-late afternoon as the boundary approaches and shortwave moves through. Large MUCAPE 2000+ J/kg, increasing shear profiles to around 50 kts 0-6km, and the dry low levels point towards a large hail and wind threat for early storms, including supercells possible. Of note, 18z extended HRRR does suggest that a couple of supercells may track across N IA while most larger scale guidance suggested initiation and track further N. Evolution into the evening remains likely that additional convection will congeal into a progressive MCS with the main severe threat damaging winds as the LLJ increases. The overall track also continues likely be mostly N and E of the forecast area, following mean flow across southern MN and then turning SE into S WI. Backbuilding to the SW will be dependent on both the strength of outflow and the LLJ. Even so, confidence is not great that significant expansion will be seen into central Iowa at this time. As the boundary sags southward Friday AM, additional decaying activity may be seen from storms streaming in from prior LLJ activity in NE. Most activity Friday/Saturday should remain south of the state as the boundary settles into MO. After Thursday/Thursday PM, next opportunity will be Sunday with synoptics remaining in fair agreement on fairly widespread precipitation along/ahead of a cool/cold front and larger upper trough passage. Any strong/severe potential remains difficult to hone in on and will be hashed out in the coming days. Beyond Sunday, chances remain in flux with the 12z deterministics trending dryer than previous runs. Ensembles too look to have trended drier next week, unfortunately. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 700 PM CDT Wed Jun 16 2021 Expecting VFR conditions for the majority of the TAF period. There is the potential for some convection later tonight into the overnight hours. If a storm does happen to pass over a TAF site, there is the potential for visibility restrictions with some decent rainfall. High LCLs tonight thought should keep ceilings VFR. && .DMX WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 1 PM to 8 PM CDT Thursday for IAZ033>036- 044>048-057>061-070>075-081>086-092>097. && DISCUSSION...Curtis AVIATION...Podrazik
Hazardous Weather Outlook National Weather Service Des Moines IA 335 PM CDT Wed Jun 16 2021 IAZ033>036-044>048-057>061-070>075-081>086-092>097-172045- Sac-Calhoun-Webster-Hamilton-Crawford-Carroll-Greene-Boone-Story- Audubon-Guthrie-Dallas-Polk-Jasper-Cass-Adair-Madison-Warren- Marion-Mahaska-Adams-Union-Clarke-Lucas-Monroe-Wapello-Taylor- Ringgold-Decatur-Wayne-Appanoose-Davis- 335 PM CDT Wed Jun 16 2021 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Tonight There is a marginal risk for some severe thunderstorms late tonight into early Thursday morning. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday A Heat Advisory is in effect for the are Thursday. Please refer to the National Weather Service website at weather.gov/desmoines for further details. Thunderstorm chances return to the forecast again Thursday afternoon into Thursday night. Storms may be strong to severe Thursday with hail and gusty winds the primary threats. The most favorable area for severe storms will reside across north central into eastern Iowa. Thunderstorm chances return to the forecast again Additional storms are possible Sunday and again Monday. The threat for severe weather early next week is uncertain at this time. .SPOTTER INFORMATION STATEMENT... Spotters may be needed Thursday afternoon and night. IAZ004>007-015>017-023>028-037>039-049-050-062-172045- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Hardin-Grundy- Black Hawk-Marshall-Tama-Poweshiek- 335 PM CDT Wed Jun 16 2021 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Tonight There is a marginal risk for some severe thunderstorms late tonight into early Thursday morning. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thunderstorm chances return to the forecast again Thursday afternoon into Thursday night. Strong to severe thunderstorms are becoming more likely Thursday into Thursday night with hail and gusty winds the primary threats. The most favorable area for severe storms will reside across north central into eastern Iowa. Additional storms are possible Sunday and again Monday. The threat for severe weather early next week is uncertain at this time. .SPOTTER INFORMATION STATEMENT... Spotters may be needed Thursday REV
The Des Moines radar (KDMX), 159 km away, was scanning. The volume nearest the first event began at 02:08 UTC.
9 thunderstorm wind, 3 hail, 1 high wind. Local standard time, as filed.
Public report of 60 mph winds accompanied by 10 minutes of hail from pea to dime sized.
Numerous three to six inch tree limbs were downed across Schaller with one twelve inch diameter branch snapped off. Power was out for some time. Time estimated via radar.
Dim to quarter sized hail laying on the ground behind the storm at US Highway 20 and Highway 110. Time estimated via radar.
A trained spotter reported ping pong ball sized hail.
Public report via mPING of penny sized hail.
A trained spotter reported a healthy thirteen inch diameter tree limb down. Time estimated via radar.
The fire department reported numerous twelve to sixteen inch diameter tree limbs down throughout Odeboldt, blocking roads and knocking out power. A few of the limbs were reported to have rotten centers.
A personal weather station KIACARRO21 recorded a 59 mph gust.
A trained spotter reported a large tree down on a house and garage while also pulling down power lines. Other two to six inch diameter branches down and a flag pole blown over.
Personal weather station KIACARRO16 reported a 62 mph gust.
Personal weather station KIAMANNI6 reported a 60 mph wind gust.
A tree was downed, blocking Iowa Highway 141 west of US Highway 59.
Strong wind gust occurred behind thunderstorms, in what was likely a wake low scenario.
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, June 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: 957872, 957879, 957880, 957882, 957883, 957885, 957887, 957889, 957890, 957891, 957892, 957893, 968633.