Dry conditions for much of the summer led to expanding drought conditions across portions of northwest and central Iowa.
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
Dry conditions for much of the summer led to expanding drought conditions across portions of northwest and central Iowa.
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 17, 10:35 PM CST, 1 hour 25 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1135 PM CDT Mon Aug 17 2020 ...Updated for 06z Aviation... .SHORT TERM.../Tonight through Tuesday Night/ Issued at 301 PM CDT Mon Aug 17 2020 Confidence: High Current weather the most challenge and generally quiet after sunset through Tuesday night. Weak low and trailing trough moving through eastern Iowa into Illinois/Indiana by 00z tonight. Winds have been mixing to near 30 mph at times behind the trough with clouds filling in due to enhanced lift. Across the southeast near Ottumwa, still a chance of a brief shower/iso thunder into late afternoon early evening. Otherwise tonight winds will decouple and skies should clear with cooler temperatures. H850 "cool" air advection increasing now with temperatures aloft bottoming out around 06z then rising slowly west as the ridge axis drifts a bit east by 12z. Cool overnight mins in the lower 50s northeast to the mid/upper 50s central and west. On Tuesday, temperatures will remain cooler east/northeast with warmer readings expected west. While the ridge/high will persist over the Great Lakes through Wednesday morning, an area of low pressure will develop in the Plains resulting in some showers over far northwest Iowa by 12z Wednesday. Tuesday night will see some increase in clouds late with a similar distribution of cooler east/milder west. Highs Tuesday will range from the upper 70s/low 80s east to the lower 80s west during the day. Lows Tuesday night will rise a about 5 degrees to upper 50s to around 60. .LONG TERM.../Wednesday through Monday/ Issued at 301 PM CDT Mon Aug 17 2020 /Wednesday through Friday/ Confidence: Medium to High Other than a warming trend into late week along with some chances for thunderstorms over the northwest/west in a zone of more persistent warm air advection, the overall pattern appears to be generally less active. Given the persistent southwest flow aloft, it's likely that low level moisture will again return to much of the region by Friday; especially to the west and north of Iowa. Highs in the period will reach the mid to upper 80s/near 90 by Friday with lows climbing into the 60s most areas. /Friday Night through Monday/ Confidence: Medium Confidence will lessen into the weekend due to a number of factors. A frontal boundary will be nearing northern Iowa Saturday morning. Storms should fire Friday night over South Dakota and Minnesota, possibly working south into northern Iowa early Saturday. Wind shear could be just strong enough to organize storm structure with forcing and a weak short wave also suggesting convection may continue into the morning hours as the convection swings east along the sfc boundary. Uncertainty in the boundary placement in the GFS vs. the Euro will be determined in the coming days. Currently the general consensus is over far northern Iowa or southern Minnesota. Both models eventually drive the boundary farther south by 06z Sunday as convection helps nudge the wave and trailing cold front farther south. Differences remain into Monday as the GFS refrain from any additional cooling following the boundary while the Euro cools the area into Monday. Currently the forecast reflect the warmer solutions. && .AVIATION.../For the 06Z TAFS through 06Z Tuesday night/ Issued at 1135 PM CDT Mon Aug 17 2020 VFR conditions will persist through the TAF period. Patchy fog is possible across northwest Iowa early Tuesday morning, however this should not impact any sites, though it could get close to KFOD. Otherwise, winds tomorrow will gradually shift from northwesterly to east or southeasterly by Tuesday afternoon and evening. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...REV LONG TERM...REV AVIATION...Hagenhoff
Hazardous Weather Outlook National Weather Service Des Moines IA 300 PM CDT Mon Aug 17 2020 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-182000- 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- 300 PM CDT Mon Aug 17 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday There will be a slight chance for thunderstorms Thursday night as well as late Friday into Saturday. The severe potential will be better determined in the coming days. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. Zogg
The national radar mosaic for the moment the first event began.
5 drought. Local standard time, as filed.
Slight above normal temperatures and lack of rainfall led to expansion of severe drought conditions into Palo Alto county in mid August.
Slight above normal temperatures and lack of rainfall led to expansion of severe drought conditions into Kossuth county in mid August.
Slight above normal temperatures and lack of rainfall led to expansion of severe drought conditions into Humboldt county in mid August.
Slightly above normal temperatures and lack of rainfall led to expansion of severe drought conditions into Wright county in mid August.
Slightly above normal temperatures and lack of rainfall led to expansion of severe drought conditions into Hardin county in mid August.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyWarnings in Iowa, August 2020
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: 915650, 915651, 915652, 915653, 915654.