Heavy rainfall in areas of northern Iowa and southern Minnesota on August 27th and 28th allowed rivers such as the Cedar, Shell Rock, and Wapsipinicon to swell, including reaching flood state at Janesville, IA and Cedar Falls, IA. Impacts were largely minor with both sites failing to reach moderate or greater flood stage levels.
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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.
Heavy rainfall in areas of northern Iowa and southern Minnesota on August 27th and 28th allowed rivers such as the Cedar, Shell Rock, and Wapsipinicon to swell, including reaching flood state at Janesville, IA and Cedar Falls, IA. Impacts were largely minor with both sites failing to reach moderate or greater flood stage levels. While Janesville receded prior to the end of the month, Cedar Falls remained in flood stage into the first of September.
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 29, 10:53 PM CST, 1 hour 37 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1153 PM CDT Sun Aug 29 2021 ...Updated Aviation Discussion... .DISCUSSION.../Tonight through Sunday/ Issued at 223 PM CDT Sun Aug 29 2021 Forecast Highlights: -- More seasonable today, much of week. -- Chances for scattered storms late tonight into Monday morning. -- Additional storm chances Monday evening into Tuesday morning. TODAY THROUGH TUESDAY: The cold front that entered the state last night passed through central Iowa this morning and has continued to push southeastward through the state through midday. Remaining scattered showers along the front this morning lost much of their forcing as the shortwave trough lifted northeast out of the state mid-morning. This resulted in showers continuing to diminish as the front continued to move through the state. The passing cold front has decreased humidity values in northern Iowa and dropped temperatures a bit leaving more comfortable conditions in its wake across the state. High temperatures today will be back in the upper 70s northwest to mid 80s southeast. These more seasonable temperatures will continue into Monday with high temperatures remaining in the upper 70s to low 80s and lows Monday morning around/near 10 degrees cooler than this morning in the mid 50s to mid 60s. With the departure of the aforementioned shortwave, more zonal mid- level flow has returned and the cold front progression has slowed down. The cold front will ultimately stall out near the Iowa/Missouri border this evening, staying put through early Tuesday. The zonal mid-level flow pattern will continue until late Monday/early Tuesday as well when another mid-level trough develops early Tuesday with the remnants of Hurricane Ida moving northeast through the Tennessee Valley. Any direct impacts from the remnants will stay out of our area. However, shower and thunderstorm chances do return to the forecast late tonight/early Monday morning in southern Iowa and again Monday evening into Tuesday morning, potentially more widespread, with the boundary stalled out along our southern border. A push of warm air advection into southern Iowa will be the main driver of scattered non-severe convection overnight into Monday morning along the Iowa/Missouri border and into parts of southern Iowa, mainly after midnight. Much of the north half of the state will stay dry overnight with few clouds thus promoting the lows in the 50s previously mentioned. Showers/storms may linger into the southwest third to southwest half of the state on Monday morning with additional thunderstorm development later Monday as another shortwave trough passes through within the westerly mid-level flow. Current model trends suggest development on Monday evening near the Iowa/Nebraska border moving eventually eastward into our area mainly during the late evening/overnight hours Monday and lingering into Tuesday morning. The severe potential still looks to be low at this point late Monday with weak low-level shear and the LLJ mainly west of the area. There is still some uncertainty in the extent of storm progression into our area and then across the CWA into Tuesday, and current PoP trends may be a bit too progressive/robust. BEYOND TUESDAY: Mid-level ridging builds into the area late Tuesday into Thursday, offering a dry period from later Tuesday into Thursday morning before a few boundaries pass through the area into next weekend. A surface warm front on Thursday followed by a cold front that lingers into the early upcoming weekend brings renewed chances for thunderstorm activity to end the week. High temperatures look to remain in/near the 80s all week. Any severe potential will be better determined in the coming days. Will also continue to monitor the hydro threat with any additional storms this week given our recent rainfall. && .AVIATION.../For the 06Z TAFS through 06Z Monday night/ Issued at 1149 PM CDT Sun Aug 29 2021 VFR conditions look to continue through the TAF period. Only concern remains some fog potential for MCW and possibly FOD and ALO. However, low confidence with the widespread nature and the duration of the fog and thus left out mention of any MVFR conditions for the northern TAF sites. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && DISCUSSION...KCM AVIATION...Podrazik
Hazardous Weather Outlook National Weather Service Des Moines IA 337 PM CDT Sun Aug 29 2021 IAZ044-057>059-070>074-081>086-092>097-301100- Crawford-Audubon-Guthrie-Dallas-Cass-Adair-Madison-Warren-Marion- Adams-Union-Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur- Wayne-Appanoose-Davis- 337 PM CDT Sun Aug 29 2021 This Hazardous Weather Outlook is for portions of southwest Iowa. .DAY ONE...Tonight Thunderstorm chances return to the forecast late tonight. The severe weather potential is low. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorm chances are in the forecast Monday into Tuesday, and then again Thursday Night through the weekend. The severe weather potential is low early this week, and uncertain heading into the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation is unlikely for the time being. IAZ004>007-015>017-023>028-033>039-045>050-060>062-075-301100- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk-Carroll-Greene-Boone- Story-Marshall-Tama-Polk-Jasper-Poweshiek-Mahaska- 337 PM CDT Sun Aug 29 2021 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday Thunderstorm chances are in the forecast late Monday into Tuesday, and then again late Thursday through the weekend. The severe weather potential is low early this week, and uncertain heading into the weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation is unlikely for the time being. Small
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
Site entered flood state at 1230am LST on August 30th, crested at 15.11 ft at 845am LST on August 31st, and fell below flood stage at 1115am on August 31st.
River entered flood state at 1230pm LST on the 30th of August, crested at 91.43 ft on 215am LST on August 31st, and fell below flood stage on 815am LST on September 1st.
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, August 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: 982184, 982176.