Diurnally driven afternoon storms on Sunday, July 20th, 2025, developed within an unstable environment with CAPE values over 3000 J/kg and 40 to 45 kts of effective shear. Despite this unstable and decently sheared environment, several factors limited the severe weather potential, including weak low-level flow, a warm layer aloft, and an overall lack of forcing.
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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.
Diurnally driven afternoon storms on Sunday, July 20th, 2025, developed within an unstable environment with CAPE values over 3000 J/kg and 40 to 45 kts of effective shear. Despite this unstable and decently sheared environment, several factors limited the severe weather potential, including weak low-level flow, a warm layer aloft, and an overall lack of forcing. This led to disorganized storms that remained below severe limits. The weak flow and low-level instability did allow for the production of a few funnel clouds in western Iowa, but these remained aloft and posed no threat to lives or property. |The primary impact from these slow-moving storms was heavy rainfall over already saturated ground from the morning's events. One storm developed directly over the Des Moines metro area and slowly drifted southward, dropping an additional 1 to 2 inches of rain on top of the 3 to 4 inches that had fallen early in the day. Drainage systems were quickly overwhelmed, producing street and building flooding in Des Moines and West Des Moines, particularly in areas near the Raccoon River. Fortunately, this flash flooding was short-lived and waters receded by the late evening.
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 Jul 20, 1:45 PM CST, 2 hours 45 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Des Moines IA 245 PM CDT Sun Jul 20 2025 .KEY MESSAGES... - A few storm possible tonight, mainly over the far south and northwest. A strong storm may occur over the northwest. - Hot and humid conditions expected Tuesday and Wednesday with heat index values in excess of 100 degrees in the afternoons. - Additional storm chances arrive at the end of the week. && .DISCUSSION... Issued at 243 PM CDT Sun Jul 20 2025 Convective trends through Monday are the near term forecast challenge after the past several nights of MCSs moving across the state with some severe weather and heavy rainfall. This afternoon, much of the state is under scattered to broken stratocumulus clouds with a warm layer above keeping convection in check for the most part. There are a few isolated areas of bubbling but this has been mostly short lived. Also monitoring thunderstorms that are ongoing over eastern South Dakota with one primary supercell currently southwest of Huron. This storm should be slightly elevated and is beginning to make a turn southeast into the instability axis which would fit the conceptual model for this. This is the area to watch should stronger convection reach the area, perhaps as early as early this evening. Otherwise, not expecting much for areal coverage in storms overnight with the other focus region just south of the Iowa border into Missouri. As mentioned in the aviation discussion, stratus should move back into the state overnight and into early Monday and it could be further supported with an increasing elevated mixed layer aloft, trapping moisture below it. Some fog could develop as well though at this time, much of the moisture will support the stratus. High temperatures Monday may depend on how quickly this cloud cover can mix out on Monday. The Southern Plains upper ridge will extend lift north with ridging and thermal ridging moving into Iowa later Monday night and into Tuesday which will bring hot and humid conditions to central Iowa. Expected heat index values for Tuesday afternoon are in the 100 to 110 degree range. The current dewpoint forecast for the afternoon is in the mid to upper 70s. That may be a bit high considering the mixing potential though lower mixed dewpoints could result in high actual temperatures. Heat headlines are possible for Tuesday. Heat indicies back in the 95 to 105 range again on Wednesday. The upper ridging will move east Wednesday night into Thursday leading to southwest flow into Iowa with another short wave approaching the area and a boundary dropping into the state. This will bring the next chance for thunderstorms to the region. Those chances will be on and off into the weekend. There is the potential for even stronger upper ridging becoming re-established early next week which would bring another round of very hot conditions though being on the northeast quadrant of this feature could also lead to MCSs dropping into the state. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1228 PM CDT Sun Jul 20 2025 A large swath of stratocumulus is over Iowa early this afternoon with bases rising to MVFR while some scattering has resulted in VFR at times. Most sites should become VFR this afternoon as bases rise further. The low level steering flow comes from the southeast tonight and that is a source region of MVFR to IFR cigs that are currently over parts of Illinois and Ohio. Those cigs will move into central Iowa overnight into early Monday. Thunderstorm chances have decreased during the period therefore no mention in this forecast. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && DISCUSSION...Donavon AVIATION...Donavon
Hazardous Weather Outlook National Weather Service Des Moines IA 209 PM CDT Sun Jul 20 2025 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-211915- 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- 209 PM CDT Sun Jul 20 2025 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Isolated storms are possible (~25% chance) this afternoon into evening, mainly south, and late tonight into the overnight (~20% chance) mainly in the west to northwest. The chances for severe storms remains low at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday Isolated thunderstorms may continue into early Monday with some redevelopment possible (~15% chance) later in the day as well, especially south. Severe storms are not expected. Additional storms are possible mid to late next week. Heat builds into the area into mid-week with heat indices topping 100 degrees at times. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated.
Preliminary Local Storm Report
National Weather Service Des Moines IA
1148 AM CDT Sun Jul 20 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0545 AM Tornado 4 WNW Gilbert 42.13N 93.71W
07/19/2025 Boone IA NWS Employee
Radar confirmed tornado with a track evident
via satellite imagery. Additional analysis
and details will be determined at a later
time including rating and path length.
&&
RDThe Omaha radar (KOAX), 112 km away, was scanning. The volume nearest the first event began at 22:30 UTC.
1 funnel cloud, 1 flash flood. Local standard time, as filed.
News media KJAN has several pictures of funnel clouds near Atlantic, Anita, and Massena from Sunday evening.
Local law enforcement reported flash flooding over portions of the Des Moines metro area on the evening of July 20th 2025. Several intersections closed along 63rd Ave, with several stranded vehicles. George Flagg Parkways closed, with flooding reported in the Valley Junction area. Local media also reported deep, standing water along Ashworth road in West Des Moines.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2025Every state in 2025This day in weather historyWarnings in Iowa, July 2025
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: 1290895, 1290943.