Alert archive / Iowa / Flash Flood Warnings in 2026

Flash Flood Warning 21, NWS Des Moines, IA

July 20, 2026Jasper County, Polk County, Iowa

NWS Des Moines, IA issued this flash flood warning at Jul 20, 2026, 8:18 PM CDT for Jasper County, Polk County, Iowa. It was in force for 6 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 20, 2026, 8:18 PM CDT (01:18 UTC)
Expired: Jul 21, 2026, 2:15 AM CDT
In force: 6 hr
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Flood severity: None

Counties Jasper County, IA, Polk County, IA

The radar

The Des Moines radar (KDMX), 36 km from the middle of the area, began a volume at 01:20 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.3 hours before the alert went out and 256 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 3406 J/kg
Mixed-layer CIN: -69 J/kg
Mixed-layer LCL: 1856 m above ground
0-6 km bulk shear: 35 kt
0-1 km storm-relative helicity: 58 m²/s²
0-3 km storm-relative helicity: 104 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 5.9

Open this sounding in Storm Lab

The text

As transmitted.

179 
WGUS53 KDMX 210118
FFWDMX
IAC099-153-210715-
/O.NEW.KDMX.FF.W.0021.260721T0118Z-260721T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Des Moines IA
818 PM CDT Mon Jul 20 2026

The National Weather Service in Des Moines has issued a

* Flash Flood Warning for...
  Western Jasper County in central Iowa...
  Southeastern Polk County in central Iowa...

* Until 215 AM CDT.

* At 818 PM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 3 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Des Moines, Newton, Altoona, Pleasant Hill, Carlisle, Bondurant, 
  Colfax, Monroe, Prairie City, Baxter, Iowa Speedway, Prairie 
  Meadows, Adventureland Amusement Park, Runnells, Lambs Grove, 
  Prairie City Krohn Airport and Newton Municipal Airport.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For the latest stream observations and forecasts refer to 
weather.gov/desmoines/water.

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4151 9347 4151 9348 4173 9354 4161 9330
      4186 9315 4169 9298 4151 9309 4151 9342

FLASH FLOOD...RADAR INDICATED

$$

Jimenez

1 follow-up statement

042 
WGUS73 KDMX 210706
FFSDMX

Flash Flood Statement
National Weather Service Des Moines IA
206 AM CDT Tue Jul 21 2026

IAC099-153-210716-
/O.EXP.KDMX.FF.W.0021.000000T0000Z-260721T0715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Jasper IA-Polk IA-
206 AM CDT Tue Jul 21 2026

...FLASH FLOOD WARNING WILL EXPIRE AT 215 AM CDT EARLY THIS MORNING 
FOR WESTERN JASPER AND SOUTHEASTERN POLK COUNTIES...

Flood waters have receded. The heavy rain has ended. Flooding is no 
longer expected to pose a threat. Please continue to heed remaining 
road closures.

&&

LAT...LON 4151 9347 4151 9348 4173 9354 4161 9330
      4186 9315 4169 9298 4151 9309 4151 9342

$$

Hagenhoff

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 7:11 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marion, Polk, Warren	49 min
Jul 20, 7:35 PM CDT	Flash Flood Warning	DMX	Boone, Jasper, Marshall, Polk, Story	6 hr
Jul 20, 7:45 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marion, Polk, Warren	45 min
Jul 20, 8:21 PM CDT	Severe Thunderstorm Warning	DMX	Lucas, Mahaska, Marion, Monroe	28 min
Jul 20, 8:38 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Madison, Polk, Warren	37 min
Jul 20, 9:02 PM CDT	River Flood Warning	DMX	Polk	4 hr
Jul 20, 9:07 PM CDT	Flash Flood Warning	DMX	Dallas, Polk	6 hr
Jul 20, 9:15 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Madison, Polk, Warren	17 min
Jul 20, 9:47 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Madison, Polk, Warren	43 min
Jul 20, 9:53 PM CDT	Severe Thunderstorm Warning	DMX	Appanoose, Lucas, Monroe, Wayne	52 min
Jul 20, 10:24 PM CDT	Severe Thunderstorm Warning	DMX	Appanoose, Davis	51 min

Nearby

Flash Flood Warnings in Iowa, 2026 Every flash flood warning in 2026

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.