Alert archive / Iowa / Severe Thunderstorm Warnings in 2026

Severe Thunderstorm Warning 282, NWS Des Moines, IA

July 20, 2026Marshall County, Story County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Jul 20, 2026, 5:28 PM CDT for Marshall County, Story County, Iowa. It was in force for 47 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 20, 2026, 5:28 PM CDT (22:28 UTC)
Expired: Jul 20, 2026, 6:15 PM CDT
In force: 47 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Damage threat: Destructive
Hail: 2.75 in
Wind: 60.0 mph

Counties Marshall County, IA, Story County, IA

The radar

The Des Moines radar (KDMX), 53 km from the middle of the area, began a volume at 22:29 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 20, 3:03 PM CDT	Tornado Watch	SPC	7 hr

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 10.5 hours before the alert went out and 314 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: 982 J/kg
Mixed-layer CIN: -242 J/kg
Mixed-layer LCL: 1013 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 299 m²/s²
0-3 km storm-relative helicity: 288 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.2

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, 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 this severe thunderstorm warning went out at Jul 20, 5:25 PM CDT, 3 minutes earlier.

Area forecast discussion, Jul 20, 5:25 PM CDT, 3 minutes before

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Hazardous weather outlook, Jul 20, 2:38 PM CDT, 2 hours 50 minutes before

Hazardous Weather Outlook
National Weather Service Des Moines IA
238 PM CDT Mon Jul 20 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-211945-
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-
238 PM CDT Mon Jul 20 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

A Heat Advisory is in effect for the area today. Please refer to
the National Weather Service website at weather.gov/desmoines for
further details.

Strong to severe thunderstorms are possible this afternoon into
tonight with an Enhanced Risk (level 3 of 5) for severe storms.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Additional thunderstorms are possible Wednesday night into
Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today.

67

In the hours before

Local storm report, Jul 20, 4:56 PM CDT, 32 minutes before

Preliminary Local Storm Report
National Weather Service Des Moines IA
456 PM CDT Mon Jul 20 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0455 PM     Tornado          4 S Kamrar              42.34N 93.73W
07/20/2026                   Hamilton           IA   Law Enforcement

            Reports of Tornado on the ground.

&&

cec

Local storm report, Jul 20, 5:02 PM CDT, 26 minutes before

Preliminary Local Storm Report
National Weather Service Des Moines IA
502 PM CDT Mon Jul 20 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0502 PM     Funnel Cloud     1 ENE Story City        42.19N 93.57W
07/20/2026                   Story              IA   Trained Spotter

            Funnel Cloud.

&&

cec

Local storm report, Jul 20, 5:07 PM CDT, 21 minutes before

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Local storm report, Jul 20, 5:08 PM CDT, 20 minutes before

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Local storm report, Jul 20, 5:23 PM CDT, 5 minutes before

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Local storm report, Jul 20, 5:27 PM CDT, 1 minute before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 20, 7:35 AM CDT	Severe Thunderstorm Warning	DMX	Worth	25 min
Jul 20, 2:46 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Hancock, Humboldt, Kossuth, Wright	44 min
Jul 20, 2:51 PM CDT	Severe Thunderstorm Warning	DMX	Butler, Cerro Gordo, Franklin	39 min
Jul 20, 3:23 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Butler, Cerro Gordo, Franklin, Grundy, Hamilton, Hancock and 2 more	67 min
Jul 20, 3:24 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Black Hawk, Bremer, Butler, Franklin, Grundy	66 min
Jul 20, 3:56 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Black Hawk, Grundy, Hardin, Marshall, Tama	64 min
Jul 20, 3:57 PM CDT	Tornado Warning	DMX	Black Hawk, Butler, Franklin, Grundy, Hardin, Tama	48 min
Jul 20, 4:13 PM CDT	Severe Thunderstorm Warning	DMX	Black Hawk, Bremer	37 min
Jul 20, 4:25 PM CDT	Severe Thunderstorm Warning	DMX	Hamilton, Hardin	50 min
Jul 20, 4:34 PM CDT	Tornado Warning Tornado observed	DMX	Hamilton, Hardin	41 min
Jul 20, 4:45 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall, Poweshiek, Tama	60 min
Jul 20, 5:00 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Hamilton, Hardin, Story	45 min
Jul 20, 5:04 PM CDT	Tornado Warning	DMX	Hamilton, Hardin, Story	41 min
Jul 20, 5:44 PM CDT	Severe Thunderstorm Warning	DMX	Grundy, Hardin	31 min
Jul 20, 5:48 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall, Poweshiek, Tama	57 min
Jul 20, 5:52 PM CDT	Severe Thunderstorm Warning	DMX	Boone, Hamilton, Hardin, Story	23 min
Jul 20, 6:09 PM CDT	Severe Thunderstorm Warning	DMX	Boone, Hamilton, Hardin, Marshall, Story	51 min
Jul 20, 6:12 PM CDT	Severe Thunderstorm Warning	DMX	Jasper, Marshall, Story	48 min
Jul 20, 6:21 PM CDT	Severe Thunderstorm Warning	DMX	Boone	54 min
Jul 20, 6:34 PM CDT	Severe Thunderstorm Warning	DMX	Boone, Story	26 min
Jul 20, 6:47 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Boone, Jasper, Polk, Story	43 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2026 Every severe thunderstorm 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.