A weak frontal boundary draped itself across the state the previous day and into the 28th, oscillating roughly between northern and southern Iowa. During the morning and early afternoon of the 28th the boundary had made its way into southern Iowa, allowing storms to initiate and train in the area.
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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 weak frontal boundary draped itself across the state the previous day and into the 28th, oscillating roughly between northern and southern Iowa. During the morning and early afternoon of the 28th the boundary had made its way into southern Iowa, allowing storms to initiate and train in the area. Given the thermodynamic and wind profiles, a little bit of everything was able to occur. Ranging from flash flooding, a funnel cloud, sub-severe hail, and damaging winds. While a bit of everything occurred, it was all very low end by severe weather standards.
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 Aug 28, 2:19 PM CST, 1 hour 26 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 319 PM CDT Sun Aug 28 2016 .SHORT TERM.../Tonight/ Issued at 319 PM CDT Sun Aug 28 2016 Southerly flow in the lower levels with push of theta-e advection into the southern CWA today. Energy lifting out of the southern high plains northeastward toward the region, and push of theta-e advection helping with the development of spotty storms across the southern CWA today. Activity has increased in the past few hours with latest SPC Mesoanalysis suggesting decent CAPE in the area, but shear limited with effective values around 30kts. Therefore not anticipating much in the way of organized cells, but may see a strong storm or two with the potential for small hail or gusty winds. Given the amount of CAPE, an isolated severe storm will be possible especially in the next few hours before surface heating starts waning with sunset. Otherwise as sunset comes expect activity to diminish, but could see it pick up again late tonight as the LLJ kicks in and another push of theta-e advection sets up across the southern CWA. Therefore have kept pops across the southern third of the CWA through the night. Have mentioned fog again tonight with winds expected to be light and the increased low level moisture around. Hi-Res models suggesting pretty decent chance of development as well especially across the north where vsbys were limited Sunday morning as well. Kept temps a few degrees warmer though with the high dewpoints, therefore only expect temps to fall into the mid to upper 60s across the CWA. .LONG TERM.../Monday through Sunday/ Issued at 319 PM CDT Sun Aug 28 2016 From Monday through Tuesday the CONUS 500 mb pattern will be characterized by zonal flow along the U.S./Canadian border, a weak low pressure center over the four corners region, and nebulous flow elsewhere. An old decayed 500 mb trough will extend northeastward from the four corners low up across Nebraska and Iowa, providing broad but weak forcing for vertical ascent. Meanwhile in the lower levels a col region will develop over Iowa, resulting in very light flow. With a fairly moist airmass in place this will result in a couple of days of humid conditions, layered clouds, and showers and thunderstorms at times. No strong convection is anticipated and rain will likely be scattered and of the "popcorn" variety. Thus will maintain 20-40 POPs through this period, highest toward the south where the weak 500 mb trough will reside. By late Tuesday a 500 mb trough will be moving across Minnesota and into the Great Lakes region, with a large and strong surface high pressure system following in its wake. These two features will combine to push the cloudy and humid early week airmass southward on Tuesday night and Wednesday morning, ushering in dry and clear weather from Wednesday night into the weekend. On Friday a 500 mb ridge will build across the region but a low-level inversion and lack of mixing will prevent significant warming. Even so, winds turning to the southeast as the surface high finally departs combined with another day of airmass modification given clear skies and associated insolation should result in a slight warming trend to end the week, potentially reaching 80 degrees in some areas by Saturday. Toward the end of the long term forecast period, from Saturday night through Sunday, the weather pattern looks to become more active again as a large trough sets up over the western U.S. and we find ourselves beneath southwesterly 500 mb flow. In response an elongated surface trough will likely develop from eastern Colorado up into South Dakota by Saturday and eventually strengthen and kick out to the northeast as impulses round the base of the 500 mb trough. This should lead to several rounds of shower and thunderstorm chances over the latter part of Labor Day weekend. && .AVIATION.../For the 18Z TAFS through 18Z Monday afternoon/ Issued at 1251 PM CDT Sun Aug 28 2016 Low VFR/high MVFR CU field in place across the area this afternoon. Could see a pop-up storm around KOTM this evening, should stay south of KDSM. Otherwise SE winds becoming light overnight. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && SHORT TERM...Beerends LONG TERM...Lee AVIATION...Beerends
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 1026 AM CDT SUN AUG 28 2016 IAZ004>007-015>017-023>028-033>039-044>050-057>062-291000- 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- 1026 AM CDT SUN AUG 28 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THUNDERSTORMS REMAIN POSSIBLE MONDAY INTO TUESDAY. HOWEVER...THE SEVERE WEATHER POTENTIAL REMAINS LOW. ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST FRIDAY NIGHT INTO SATURDAY...BUT THE PREDICTABILITY OF SEVERE STORMS REMAINS LOW AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. IAZ070>075-081>086-092>097-291000- CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS- MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS- 1026 AM CDT SUN AUG 28 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TODAY AND TONIGHT ISOLATED NON SEVERE THUNDERSTORMS ARE EXPECTED TODAY INTO TONIGHT. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THUNDERSTORMS REMAIN POSSIBLE MONDAY INTO TUESDAY. HOWEVER...THE SEVERE WEATHER POTENTIAL REMAINS LOW. ADDITIONAL THUNDERSTORM CHANCES ARE FORECAST FRIDAY NIGHT INTO SATURDAY...BUT THE PREDICTABILITY OF SEVERE STORMS REMAINS LOW AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. MJB
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 425 PM CDT SUN AUG 28 2016 IAZ093-282215- RINGGOLD IA- 425 PM CDT SUN AUG 28 2016 ...LOCALIZED HEAVY RAINFALL WITH SLOW MOVING STORMS IN NORTHERN RINGGOLD COUNTY... AT 419 PM CDT...DOPPLER RADAR WAS TRACKING THUNDERSTORMS 10 MILES NORTHWEST OF MOUNT AYR. THESE STORMS WERE NEARLY STATIONARY. RAINFALL RATES OF ONE TO TWO INCHES PER HOUR ARE OCCURRING WITH THESE STORMS...WITH RADAR ESTIMATED RAINFALL TOTALS OF TWO TO ALMOST FOUR INCHES HAVING ALREADY FALLEN IN THE LAST THREE HOURS. THIS MAY LEAD TO LOCALIZED FLOODING ON SMALL STREAMS AND LOW LYING AREAS FOR THE NEXT FEW HOURS. THE NATIONAL WEATHER SERVICE WILL CONTINUE TO MONITOR THESE CONDITIONS AND ISSUE UPDATED STATEMENTS OR WARNINGS AS NECESSARY. RESIDENTS SHOULD STAY TUNED FOR ANY FURTHER UPDATES. LOCATIONS IMPACTED INCLUDE... DIAGONAL...TINGLEY AND SHANNON CITY. PRECAUTIONARY/PREPAREDNESS ACTIONS... TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THIS STORM...AND MAY LEAD TO LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED ROADWAYS. && LAT...LON 4065 9447 4084 9447 4090 9432 4090 9405 TIME...MOT...LOC 2119Z 049DEG 4KT 4083 9436 SKOW
The Des Moines radar (KDMX), 111 km away, was scanning. The volume nearest the first event began at 21:42 UTC.
1 flash flood, 1 thunderstorm wind, 1 hail, 1 funnel cloud. Local standard time, as filed.
Emergency manager reported water over several roads 2-3 miles northeast of Diagonal. Reports of up to 6 inches of rainfall in the area.
Fire department reported 6 to 8 inch tree limb down on a powerline at SW 1st and Davis Ave. Time radar estimated.
Public reported penny sized hail and estimated 55 mph winds.
Storm chaser reported a small, poorly defined funnel from an elevated storm.
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, August 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: 656450, 656451, 656453, 656454.