The state was stuck under northwest flow aloft, resulting in shortwaves aloft initiating storms. Additionally, at the surface a warm frontal boundary resided across the southwest third to half of the state during the day of the 21st and through the overnight.
Every event with a place to put it. Tap one for its entry below.
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.
The state was stuck under northwest flow aloft, resulting in shortwaves aloft initiating storms. Additionally, at the surface a warm frontal boundary resided across the southwest third to half of the state during the day of the 21st and through the overnight. Some storms initially developed during the afternoon and evening hours in the immediate vicinity of the front in southern and central Iowa and produced periods of heavy rainfall. Storms primarily resulted in heavy rainfall and a couple of severe wind reports. The primary action initiated late in the evening across the northwest third of the state, in the vicinity of the warm front as it moved northward. Given northwest steering flow and a nearly station surface front, storms trained through the evening and resulted in rainfall totals as high as 3.71 inches.
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 21, 3:05 AM CST, 55 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 405 AM CDT TUE JUN 21 2016 .SHORT TERM.../Today/ Issued at 405 AM CDT Tue Jun 21 2016 Ongoing thundershowers look to persist over the far southwest to south-central portion of the forecast area through roughly 12z to 14z. Deep moisture convergence and fairly strong moisture transport looks to persist into this area during the remainder of the overnight hours. There are some pockets of brief heavy rain, but little to no lightning present, and they remain progressive and scattered enough to not be too concerned for flash flooding attm. Even though this broken line extends back into central Nebraska and certainly some training seems possible prior to 12-14z this morning. The severe threat looks minimal and only concern would be for some elevated brief hail with the decent effective shear present over far southwest Iowa and enough mid-level instability to keep an updraft going long enough to produce some hail. For the rest of the day...a surge of elevated theta-E advection looks to push the front draped across NW Missouri into SE Nebraska north-northeast through the afternoon hours. There will be a brief break in storms mid to late morning before redevelopment occurs with the WAA regime this afternoon. There is low potential for the elevated convection this afternoon to spawn some isolated severe storms in the form of hail and even wind. A decent cap remains in tact, the low level shear remains weak, and the MUCAPE rises to 1000- 1500 J/kg. DCAPE values range around 300-1400 J/kg, somewhat conducive for wind, plus the deep layer shears ranges around 50 knots. Albeit there are not too many parameters in favor of severe storms this afternoon, but enough to not completely rule out an isolated severe storm or two prior to 00z Wednesday. The only hires models that depicts storms developing during the afternoon is the ARW-NMM East WRF. The NAM12 shows a little convection across the northwest by 21z. Hence, kept pops generally under 40 percent until after 22z. .LONG TERM.../Tonight through Monday/ Issued at 405 AM CDT Tue Jun 21 2016 Very active conditions are expected tonight with strong warm advection and moisture transport into the state. A low level jet of 40-50kts will focus into the northeast half of the state tonight with deep moist convection expected. Convection is expected to rapidly expand during the evening as the low level jet begins to intensify near sunset or shortly thereafter. Convection will be mostly elevated with overall area lift slowly northeast with time, although individual cells will likely drop east southeast as upper flow remains west northwest. Given the strong orthogonal inflow, heavy rain looks likely and will address the subject in the hydro section below. Otherwise, instability will be sufficient for large hail production and some damaging winds gusts and a large portion of central into northeast Iowa has been highlighted for a slight risk of severe weather late this afternoon into tonight. This whole area of convection will continue to lift to the north and east into Wednesday as better low level convergence and moisture transport move into Wisconsin and Illinois. This will end the thunderstorm threat across much of central Iowa by Wednesday morning, however some residual threat will continue in the northeast closest to the low level boundary. By afternoon, much of the forecast area will be capped off with hot temperatures into southern Iowa where thermal ridge will be overhead. There still may be a small window for severe convection in the northeast near Waterloo in the early afternoon ahead of surface low, but the bulk of severe weather will be east of the forecast area on Wednesday. The system will pass by Wednesday night with cooler and drier conditions on Thursday into early Friday. Warm advection will begin into Friday ahead of the next system with some threat of convection, albeit isolated and without a great focus at this point. A better threat of convection is expected over the weekend as a front sweeps through the state Saturday night with cooler readings into early next week. && .AVIATION.../For the 06Z TAFS through 06Z Tuesday night/ Issued at 1156 PM CDT Mon Jun 20 2016 High confidence in VFR conditions through at least mid-afternoon Tuesday. 12z TAF and especially 18z TAF will have to address thunderstorm forecast for Tuesday evening into Wednesday morning. Thunderstorms may impact all TAF sites different intervals from 22z Tue into 12z Wed. && .HYDROLOGY... Issued at 405 AM CDT Tue Jun 21 2016 Conditions certainly becoming more favorable for heavy rainfall across the northeast half of the forecast area tonight. Strong moisture advection is expected into the state overnight on nose of 40-50kt low level jet. PWATS of nearly 2" are expected to push into central and northern Iowa during the night with relatively deep warm cloud layer of over 12kft. The moist low level inflow will be nearly orthogonal to the storm movement with training becoming a possibility overnight. Therefore, sustained heavy rainfall seems quite possible tonight with the potential for some flash flooding. Some of the areas in the north and east have seen heavy rainfall over the past week or two, therefore conditions are somewhat moist, albeit becoming somewhat spotty farther south. The northeast half of the forecast area will need to be monitored for possible flash flood watch overnight if confidence continues to grow. && .DMX Watches/Warnings/Advisories...None. && SHORT TERM...Podrazik LONG TERM...Cogil AVIATION...Kotenberg HYDROLOGY...Cogil
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 533 AM CDT MON JUN 20 2016 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-211045- 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- 533 AM CDT MON JUN 20 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT A MARGINAL RISK FOR SEVERE STORMS IS FORECAST FOR SOUTHERN IOWA TONIGHT. SOME ISOLATED LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE. LOCALLY HEAVY RAIN POTENTIAL ALSO EXIST ALONG AND SOUTH OF HIGHWAY 34. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY A SLIGHT RISK FOR SEVERE STORMS IS FORECAST FOR TUESDAY AFTERNOON INTO TUESDAY NIGHT...THEN AGAIN ON WEDNESDAY. LARGE HAIL AND DAMAGING WINDS WILL BE THE MAIN THREATS...BUT ISOLATED TORNADOES CANNOT BE COMPLETELY RULED OUT. HEAVY RAIN IS ALSO LIKELY AND MAY LEAD TO AREAS OF FLASH FLOODING OR RIVER FLOODING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAYBE NEEDED AT TIMES TODAY THROUGH WEDNESDAY. KLP
The Des Moines radar (KDMX), 142 km away, was scanning. The volume nearest the first event began at 09:59 UTC.
18 heavy rain, 3 hail, 2 thunderstorm wind, 2 flash flood, 1 lightning. Local standard time, as filed.
CoCoRaHS observer 2 SE Waterloo Regional Airport reported heavy rainfall of 2.73 inches over the last 24 hours.
Mason City ASOS station recorded heavy rainfall of 2.10 inches over the last 24 hours.
Waterloo airport ASOS station recorded heavy rainfall of 2.42 inches over the last 24 hours.
CoCoRaHS observer reported heavy rainfall of 2.36 inches over the last 24 hours.
Coop observer reported heavy rainfall of 2.25 inches over the last 24 hours.
CoCoRaHS observer recorded heavy rainfall of 2.48 inches over the last 24 hours.
Mesonet station recorded heavy rainfall of 3.04 inches over the last 24 hours.
Mesonet station in Panora recorded heavy rainfall of 2.20 inches over the last 24 hours.
Mesonet station in Cedar Falls recorded heavy rainfall of 2.56 inches over the last 24 hours.
Mesonet station in Fertile recorded heavy rainfall of 2.44 inches over the last 24 hours.
Mesonet station in Waterloo recorded heavy rainfall of 2.48 inches over the last 24 hours.
Mesonet station in Cedar Falls recorded heavy rainfall of 2.84 inches over the last 24 hours.
Mesonet station in Fertile reported heavy rainfall of 2.65 inches over the last 24 hours.
Report via social media.
Trained spotter reported heavy rainfall of 1.10 inches. Heavies rain fell between 2129 and 2140 CDT.
Penny to nickel hail was reported.
Public reported heavy rainfall of 3.50 inches. Beginning time radar estimated.
Quarter size hail was reported lasting a long time, and then heavy rain after.
Public reported heavy rainfall of 3.25 inches between midnight and 8am. Reported via social media.
Trained spotter reported storm total heavy rainfall of 3.20 inches from midnight to 5 am.
Public reported heavy rainfall of 3.71 inches. Report via social media. Beginning time radar estimated.
Algona airport AWOS measured wind gust of 59 mph.
Emergency Manager reported several gravel roads throughout Butler County had water flowing over them, plus a blacktop, C13 outside of Greene, had deep water flowing over it. Time estimated by the Emergency Manager, between 2-3 am.
Law Enforcement reported a large tree branch downed onto a law enforcement vehicle.
Emergency Manager reported a house fire due to a lightning strike.
Public reported portions of University Ave from Cedar Falls to Waterloo impassable.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2016Every state in 2016This day in weather historyWarnings in Iowa, June 2016
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: 633838, 633840, 633841, 633842, 633843, 633844, 633848, 633849, 633851, 633852, 633853, 633854, 633855, 635542, 633833, 635532, 633850, 635543, 633845, 633846, 633856, 633834, 633835, 633837, 635540, 633847.